<Tr> <Td_colspan="8"> <P> When Leo is chosen for a mission over Spin, Spin recruits Bob to join him on an unauthorized mission to prove themselves . They both end up stuck in quicksand and call Leo to save them . After Leo rescues them, Donald decides to move Leo up a color . Meanwhile, Principal Perry returns saying that she wants a job as head of security at the academy . After countless attempts, Donald agrees, leaving Leo in a particular despair . Meanwhile, Sebastian tries to help Chase get revenge on Adam with a virtual reality machine . After that, Chase tells him about his creator and how they took him out . Later, Sebastian injures Donald with the machine used to prank Adam . When the Lab Rats take Donald to the medic, Sebastian turns evil and says that if they took away his father, then he is going to take away theirs . </P> Guest stars: Maile Flanagan as Perry, Max Charles as Spin, Brandon Salgado - Telis as Bob, Cole Ewing as Sebastian, Chris Grabher as Charlie </Td> </Tr> <P> When Leo is chosen for a mission over Spin, Spin recruits Bob to join him on an unauthorized mission to prove themselves . They both end up stuck in quicksand and call Leo to save them . After Leo rescues them, Donald decides to move Leo up a color . Meanwhile, Principal Perry returns saying that she wants a job as head of security at the academy . After countless attempts, Donald agrees, leaving Leo in a particular despair . Meanwhile, Sebastian tries to help Chase get revenge on Adam with a virtual reality machine . After that, Chase tells him about his creator and how they took him out . Later, Sebastian injures Donald with the machine used to prank Adam . When the Lab Rats take Donald to the medic, Sebastian turns evil and says that if they took away his father, then he is going to take away theirs . </P> <Table> <Tr> <Th> No . overall </Th> <Th> No. in season </Th> <Th> Title </Th> <Th> Directed by </Th> <Th> Written by </Th> <Th> Original air date </Th> <Th> Prod . code </Th> <Th> U.S. viewers (millions) </Th> </Tr> <Tr> <Th> 69 </Th> <Td> </Td> <Td> "Bionic Rebellion" </Td> <Td> Guy Distad </Td> <Td> Chris Peterson Bryan Moore Mark Brazill </Td> <Td> March 18, 2015 (2015 - 03 - 18) </Td> <Td> 403 / 404 </Td> <Td> 0.86 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Sebastian has secretly formed an evil rebellion to get revenge on the Lab Rats for destroying his father . Meanwhile, Leo is trapped with the other bionic people who also want revenge, but Leo manages to convince Spin and Bob to help him, and, in the end, Sebastian is defeated, his rebellion is brought down, and he and his comrades are taken to a facility . Meanwhile, Donald successfully convinces the others that he has the best interest for them at heart while Adam still blames Chase for everything that happened after the rebellion is over . </P> Guest stars: Maile Flanagan as Perry, Max Charles as Spin, Brandon Salgado - Telis as Bob, Cole Ewing as Sebastian, Marissa Cuevas as Lexi </Td> </Tr> <Tr> <Th> 70 </Th> <Td> </Td> <Td> "Left Behind" </Td> <Td> Hal Sparks </Td> <Td> Julia Miranda </Td> <Td> March 25, 2015 (2015 - 03 - 25) </Td> <Td> 401 </Td> <Td> 0.64 </Td> </Tr> <Tr> <Td_colspan="8"> <P> After sneaking some students off the island and to the mainland, the Lab Rats accidentally leave Spin and Bob behind and must retrieve them before Donald finds out . Meanwhile, Donald tries on Chase's mission suit and he and Leo scramble to get it off before Chase gets home . </P> Guest stars: Max Charles as Spin, Brandon Salgado - Telis as Bob </Td> </Tr> <Tr> <Th> 71 </Th> <Td> </Td> <Td> "Under Siege" </Td> <Td> Victor Gonzalez </Td> <Td> Ken Blankstein </Td> <Td> April 1, 2015 (2015 - 04 - 01) </Td> <Td> 402 </Td> <Td> 0.66 </Td> </Tr> <Tr> <Td_colspan="8"> <P> When suspicious events happen overnight on the bionic island, everyone is convinced a new threat has emerged . However, this threat is revealed to be Leo, when his bionics glitch because Douglas never gave Leo a capsule . </P> <P> Guest stars: Maile Flanagan as Perry, Jeremy Kent Jackson as Douglas, Grace Kaufman as Kerry Perry </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 72 </Th> <Td> </Td> <Td> "Bionic Dog" </Td> <Td> Guy Distad </Td> <Td> Mark Brazill </Td> <Td> April 8, 2015 (2015 - 04 - 08) </Td> <Td> 412 </Td> <Td> 0.79 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Adam brings a dog back to the island and Douglas reveals that it's his old dog, Otis, who Douglas made bionic in order to save his life when Otis was injured . Chase turns out to be allergic to dogs as he starts sneezing, so Douglas says that Otis has to leave, but he and Adam actually hide the dog . Meanwhile, Leo gets a new smartphone application assistant named Shelly, with whom he has fallen in love . Bree finds out and tells Leo how unhealthy it is . When Leo leaves, Bree tries to delete Shelley, but accidentally changes the settings from Shelley to Liam and is soon seduced by him . Leo hears Liam talking and realizes that Bree changed Shelly into Liam, and gets mad . Suddenly, there is an explosion in the weapons storage area and Douglas is injured . Adam, Chase, and Otis go to the weapons storage area and help Douglas up and Chase finds a tripwire . Chase goes to review the footage of the weapons storage area and shows Douglas and Adam that it was Otis who set the tripwire . Douglas and Adam don't believe him at first, saying that Chase is jealous of Otis and made the footage up . After a while, Otis goes to Adam and activates his Override App, which makes Otis able to control Adam . Douglas and Chase try to stop Adam from acting crazy . When Otis starts shooting heat rays from his eyes at Douglas and acting hostile, Chase scans Otis' bionic chip and tells Douglas that he has an override ability . Douglas says it must have been Krane who reprogrammed Otis to destroy Douglas after he betrayed Krane. Douglas is able to extract the chip from Otis . Bree and Leo come out of a room still fighting and they accidentally drop the phone . Otis pees on the phone, which short circuits it and causes Bree and Leo to stop fighting and walk away from the phone . </P> <P> Guest star: Jeremy Kent Jackson as Douglas </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 73 </Th> <Td> 5 </Td> <Td> "Mission Mania" </Td> <Td> Jody Margolin Hahn </Td> <Td> Hayes Jackson </Td> <Td> April 15, 2015 (2015 - 04 - 15) </Td> <Td> 405 </Td> <Td> 0.59 </Td> </Tr> <Tr> <Td_colspan="8"> <P> The Lab Rats are on a mission to save people from a wildfire; when the people start to chant Adam, Bree, and Chase's names, Leo gets jealous and wants to become known . Douglas gets put in charge to develop a new technology for the academy, but can only come up with things that can hurt the students . Douglas gets an idea for a lie - detecting chair . If a person lies, they are spun in the chair at mach speed . Bob then unintentionally annoys Douglas by suggesting ideas for things that have already been invented . Later, the Lab Rats get a mission alert . When they arrive at the site, they find an old lady who claims her cat ran up a tree, but it is actually a raccoon . Her cat is on the ground next to her . Then five more mission alerts come up . Back at the academy, after 15 straight missions and none of which were actual emergencies, Adam, Bree, and Chase find out that Leo had made 10,000 business cards and a commercial in English and Spanish for a bionic emergency rescue service . Getting mission alerts from all over the country, Chase decides not to go because at least half of the alerts are not emergencies . Leo feels he needs to fulfill his promises and save people, so he goes on a mission alone . As Bob continues to drive Douglas crazy, he and Spin see all the mission alerts and start answering calls . Arriving at the mission site, Leo finds a helicopter about to fall over a side of a building . Using his super strength, he tries to pull the helicopter back down, but it is too heavy . Calling Bob for help, Leo gets put on a 20 - minute hold . Adam starts to help Spin and Bob answer calls and picks up Leo's second call, but hangs up . Chase finds out from Adam that Leo called and rushes to the site of Leo's call . Arriving with Adam and Bree, Chase stabilizes the helicopter, while Bree helps the passengers out . When she goes back to check for anyone else, her suit gets stuck and the helicopter starts to fall . Leo grabs a hold of her just in time and realizes that it is not about the fame, but about saving lives . Douglas uses the technology from the lie - detecting chair to tell if the mission alerts are real or not . </P> <P> Guest stars: Jeremy Kent Jackson as Douglas, Max Charles as Spin, Brandon Salgado - Telis as Bob </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 74 </Th> <Td> 6 </Td> <Td> "Simulation Manipulation" </Td> <Td> Victor Gonzalez </Td> <Td> Greg Schaffer </Td> <Td> April 22, 2015 (2015 - 04 - 22) </Td> <Td> 406 </Td> <Td> 0.50 </Td> </Tr> <Tr> <Td_colspan="8"> Adam and Chase each lead their own student groups against each other in a series of simulated exercises that will evaluate both student and mentor performance . However, after Chase's group fails at defeating the exoskeleton and defusing a virtual bomb, Chase decides to find a way to cheat and win . He tries to use his Override App to make his group do whatever he is thinking . However, it malfunctions and they mirror what Chase does instead . With no time to fix it, the third test starts . The test is a virtual maze that the students must do alone . While watching the students' progress on the screen, Chase mimics the maze, claiming it's his good luck dance . Chase's team wins, but Adam steps on Chase's foot to expose the Override App . Chase is then punished by Donald having Adam use the Override App on Chase . However, when Adam uses it to hurt Chase, Adam hurts himself in the process . Meanwhile, Leo wakes up to find the mentor quarters a mess . After cleaning up for six hours, he blames Adam and Chase . However, when he finds the quarters a mess again, he looks at the security footage and realizes that Bree is making the mess . Leo catches Bree in the act and Bree says that she just wanted to let loose because she had some freedom . The two start throwing junk at each other; when Leo is about to bury Bree in Adam's workout clothes, she stops him and wishes there was a way she could be messy and not have Leo clean up after her . Much to Donald's dismay, they use the exoskeleton as their cleaner . </Td> </Tr> <Tr> <Th> 75 </Th> <Td> 7 </Td> <Td> "Forbidden Hero" </Td> <Td> Victor Gonzalez </Td> <Td> Steve Joe </Td> <Td> July 1, 2015 (2015 - 07 - 01) </Td> <Td> 408 </Td> <Td> 0.33 </Td> </Tr> <Tr> <Td_colspan="8"> <P> When Leo is injured during a mission, Tasha rushes to the academy to take care of him . After finding out what happens on missions, she bans Leo from joining any more missions, but he disobeys her and goes on a mission with the rest of the team . When Tasha finds out, she kicks Leo off the team and tells him that he is moving back to Mission Creek . Meanwhile, Caitlin also appears and Bob immediately becomes attracted to her . Bree tells Chase that she is mature now, but she fights over Bob . In the end, Bob tells Bree he only liked Caitlin to see if Bree liked him . Later, Tasha and the Lab Rats are having a home - cooked dinner in the mentors' quarters . Suddenly, a category five hurricane comes in . Bree and Chase rush down to help the students . Tasha thinks it is another trick and almost dies . Leo rescues her and proves that he has a place on the team . </P> <P> Guest stars: Angel Parker as Tasha, Brandon Salgado - Telis as Bob, Michaela Carrozzo as Caitlin </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 76 </Th> <Td> 8 </Td> <Td> "Spider Island" </Td> <Td> Hal Sparks </Td> <Td> Julia Miranda </Td> <Td> July 8, 2015 (2015 - 07 - 08) </Td> <Td> 409 </Td> <Td> 0.50 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Chase and Douglas reanimate a prehistoric sea spider . It escapes and bites Adam, which poisons him . It then grows and becomes 50 feet long due to growth hormones that had been given to it by Douglas . Everyone tries to stop the spider so they can create a cure for Adam . </P> <P> Guest star: Jeremy Kent Jackson as Douglas </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 77 </Th> <Td> 9 </Td> <Td> "Spike vs. Spikette" </Td> <Td> Victor Gonzalez </Td> <Td> Jason Dorris </Td> <Td> July 15, 2015 (2015 - 07 - 15) </Td> <Td> 407 </Td> <Td> 0.69 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Douglas finds out that there is a student named Kate with the Commando App . Chase tries to activate her Commando App, named Spikette by Douglas, so he can research her . When he starts fighting with Adam, she activates her Commando App and thinks Chase is her baby . While she destroys the bionic academy, Bree forces Chase to activate his Commando App by embarrassing him so he and Kate can battle . Unfortunately, he teams up with her . Douglas gives Bree a Commando App and she and Kate begin battling each other . Bree wins and Douglas extracts Kate's chip . Chase apologizes to Kate and finds out that Douglas replaced her Commando App with sonic screaming . </P> <P> Guest stars: Jeremy Kent Jackson as Douglas, Liana Ramirez as Kate, Mar Mar as Reggie </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 78 </Th> <Td> 10 </Td> <Td> "Lab Rats vs. Mighty Med" </Td> <Td> Rich Correll </Td> <Td> Mark Brazil Vincent Brown Clayton Sakoda Ian Weinreich </Td> <Td> July 22, 2015 (2015 - 07 - 22) </Td> <Td> 415 </Td> <Td> 1.07 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Chase and Donald have invented a new technology that takes in energy from any environment . Chase feels that he does not get his share of spotlight when Donald sells the product without his approval . Meanwhile, Kaz comes to the bionic academy to get powers, bringing Oliver with him . Chase decides to make a deal with another company when its CEO comes to buy the product . The person turns out to be a villain called the Incapacitator, who wanted to steal the product for his own use . The Lab Rats find out that Kaz and Oliver are not bionic heroes . Tecton, Gamma Girl, and Grey Granite arrive when finding out that the Incapacitator has come here . Leo has the same energy transfer power as the Incapacitator . The Lab Rats later find out they are real superheroes . The Incapacitator blasts and injures Chase . Kaz, Oliver, and the other Lab Rats take him to Mighty Med . Kaz switches brains with Chase to find out what problems Chase has . Chase's injury has created a hardware virus in his bionic chip, causing the chip to generate plutonic energy . He is stable for now, but if his blood pressure gets too high...he will explode . Meanwhile, the others go to find the Incapacitator . Skylar tries to get in the middle of the romance that Bree and Oliver form . They go to the Eiffel Tower to find that he is in Las Vegas . Kaz tricks the Incapacitator to absorb Chase's virus and the Incapacitator explodes . Chase and Kaz switch brains back and Bree stops liking Oliver after she finds out that he resembles Chase . The Lab Rats then depart from Mighty Med hospital to go back home . </P> <P> Starring: Billy Unger, Spencer Boldman, Kelli Berglund, Tyrel Jackson Williams, Hal Sparks, Bradley Steven Perry, Jake Short, Paris Berelc </P> <P> Guest stars: Jilon Vanover as Tecton, Damion Poitier as Incapacitator, Carlos Lacámara as Horace </P> Note: This is a combined special episode for both Lab Rats and Mighty Med . (See also: Lab Rats: Elite Force .) </Td> </Tr> <Tr> <Th> 79 </Th> <Td> 11 </Td> <Td> "Space Elevator" </Td> <Td> Hal Sparks </Td> <Td> Jonah Kuehner </Td> <Td> July 29, 2015 (2015 - 07 - 29) </Td> <Td> 414 </Td> <Td> 0.64 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Donald's top scientist, Dr. Ryan, arrives to test Chase's invention . The two of them dislike each other and don't get along . When Donald puts Dr. Ryan in charge of the space elevator, Chase immediately gets jealous . Donald then makes Chase Dr. Ryan's assistant . Dr. Ryan puts Chase in charge of screwing in the lug nuts, but Chase refuses, and Dr. Ryan builds the space elevator without Chase . The day of the launch, Chase performs a bionic scan of the elevator and finds a major braking flaw on the elevator . Chase tells Leo and they agree to keep it to themselves . Donald then decides not to use the test dummy and says that he should test out the space elevator . Chase and Leo try to convince Donald to not go, but he can't hear them since the space elevator's walls are soundproof . After the space elevator takes off, Chase tells Dr. Ryan that there is a design flaw with the braking system . The two of them work together to safely get Donald back on the ground . Working together they reversed the charge and the elevator begins coming down ten times as fast . Leo decides to stand under the elevator to stop it from hitting the ground and killing Donald . His plan works until Donald approaches all of them and tells them that he used the emergency parachute to escape . Leo then gets stuck holding the space elevator until he tries to escape and it drops, crushing his leg . His leg is broken so badly that he needed a titanium rod put in . Instead, Donald does the procedure himself and gives Leo a bionic leg . </P> Guest stars: Maile Flanagan as Perry, Brandon Salgado - Telis as Bob, Mark Saul as Dr. Ryan </Td> </Tr> <Tr> <Th> 80 </Th> <Td> 12 </Td> <Td> "Bionic Action Hero" </Td> <Td> Victor Gonzalez </Td> <Td> Hayes Jackson Ken Blankstein </Td> <Td> August 5, 2015 (2015 - 08 - 05) </Td> <Td> 410 / 411 </Td> <Td> 0.97 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Douglas tells the group that his old college ex-girlfriend, a film director named Giselle, will be making a film titled Bionic Action Hero based on all of them and starring an up - and - coming actor named Troy West . Giselle and Troy visit the island to learn about the bionic team . Bree immediately falls for Troy . Douglas mentions to Giselle who Marcus was and says he was Douglas' greatest invention who had the combined abilities of Adam, Bree, and Chase . Giselle is intrigued and wants to meet him, but Douglas says she can see parts of him . In the mentors' quarters, Troy explains to Bree that he needs to figure out how Chase's abilities work or Giselle will fire him from the movie . Bree uses a computer to download all the information about Chase's bionic chip and gives it to Troy . He leaves Bree behind to give the file to Giselle who conspires to eliminate the Lab Rats and start her own race of genetically modified androids . At the movie studio, Bree is still confused on why Troy blew her off . She enters his dressing room, but Giselle and Troy start to walk in . Bree turns invisible and overhears Giselle tell Troy about Chase's schematics and that they can initiate their plan when the time is right . Bree switches the laptop that was opened with the one with Chase's schematics and Giselle and Troy leave . During filming of the movie, Bree stops Troy before he can fire a blaster gun at Adam, Chase, and Leo . Bree explains to everyone that Giselle only lured them to the set to kill them . Giselle then explains to them that she wanted to get her hands on advanced android fighting machines until Adam, Bree, and Chase ruined her chances . Giselle also reveals that all of her film crew members are androids, including Troy . Giselle then mentions that, with Chase's schematics, she can give all of them super intelligence . Troy gets a hold of the blaster gun, but Bree interrupts to say if he destroys them, he destroys the laptop with Chase's schematics, though Giselle has already made backups all over her servers . Chase then hatches a plan to use a virus to destroy the servers . A battle ensues with Adam, Bree, and Leo trying to take down the androids, while Chase and Douglas manage to let the virus out and fry Giselle's servers . The androids then surround the Lab Rats and Troy sneaks up, knocks Chase unconscious, and carries him away . Giselle then hatches a plan to rip out Chase's chip . Giselle later tells them that the set is rigged with explosives . The android film crew starts geo - leaping away from the movie studio . Adam, Bree, Leo, and Douglas manage to escape by grabbing onto the androids . Douglas is unable to locate Chase because Giselle deactivated his Location App . In the lab, Giselle tells Chase that Troy is an old model and she created a newer version with androids taking the appearance of anyone of Giselle's choosing so that they can blend in with society . Douglas calls Giselle so Leo can track her location . The academy is attacked by a new android warrior . Adam and Bree escape to rescue Chase . At the lab, Adam and Bree arrive and Troy wants to be the one to destroy them while an android warrior tries to rip out Chase's chip . At the academy, Douglas reveals that the androids' off switches are located inside of their noses . At the lab, Adam and Bree battle against Giselle and Troy . At the academy, Leo deactivates the android warrior . At the lab, Adam and Bree use their bionic abilities to knock out Giselle and Troy . Adam and Bree race to Chase's side, but are too late . Adam feels guilty because all he has ever done to Chase is punch and make fun of him, but never told him that he loved him . Giselle enters and mockingly apologizes . Chase reveals to everyone that he is alive . Only Chase's android replica is on the table . Giselle unleashes more android warriors, but they are quickly destroyed by Leo and Douglas . Troy awakens and double - crosses Giselle because she was planning to get rid of him . With her out of the way, he plans on not only destroying bionic humans but also all humans . He blasts Giselle, knocking her out, and then takes Bree hostage . Bree demands for Adam to use his blast wave to take Troy out, but he refuses, saying it would take her out as well . Bree tells him that if it means saving everyone else then it is worth it . After some hesitation, Adam, Chase, and Leo get ready to attack just as Troy backs away to a sink full of water . Bree then realizes that water would destroy him and manages to break free from him and dunk him into the sink, which short - circuits him . However, Giselle manages to escape . In the end, Giselle is looking for Marcus in Douglas' old lair . </P> <P> Special guest star: Leo Howard as Troy West </P> <P> Guest stars: Jeremy Kent Jackson as Douglas, Jessalyn Wanlim as Giselle </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 81 </Th> <Td> 13 </Td> <Td> "One of Us" </Td> <Td> Guy Distad </Td> <Td> Julia Miranda </Td> <Td> August 12, 2015 (2015 - 08 - 12) </Td> <Td> 416 </Td> <Td> 0.58 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Adam, Bree, and Chase are looking for Leo because he is late for training and find out he is in Mission Creek because Janelle threatened to break up with him . S - 1 shows up unexpectedly and shocks everyone . She came to the island because, like everyone else, her memory is blank, but has continuing flashbacks of Krane . No one believes her until she suggests taking out her chip . Chase and Douglas realize that she has a doomsday virus in her because she was under the influence of the Triton App . Feeling it is worse than he thought, Chase uses his scan ability and finds out that the students, Adam, Bree, and himself also have the doomsday virus implanted in them . Bree accidentally blurts out that they are all going to die and everyone starts to panic . Chase and Douglas try to find a way to save everyone before they die . Leo comes out of the hydro - loop and attacks S - 1, unaware that she does not have any memories of their encounter, knocking her unconscious . Elsewhere, Adam and Bree are disappointed when they find out time is running out on them and they decide to have one last hurrah before they die . Adam wants to break the world record for blowing the most balloons with his pressurized lung capacity ability, while Bree wants to have a party with all of her friends from Mission Creek . S - 1 wakes up, and Leo knocks her out again out of fear . Adam does a webcast, in which he shows everyone he's breaking the record for blowing the most balloons, but Bree walks in and is upset because instead of saying, "You're all dear to me, so I'm having a party," on an invite, she mistakenly writes, "You're all dead to me, so I'm having a party ." S - 1 comes to again and relives the memory of Krane giving her the encryption code to try to destroy the virus, with Douglas playing Krane and Chase playing S - 1, to no avail . When Adam finds out how upset Bree was because she could not get her friends to come, Adam invites random strangers from the pier . Bree still wants her friends to come, but she is glad to know she has a brother who cares . Douglas and Chase are unable to find a way to stop the virus until Chase plans to have everyone temporarily die so he can give themselves doomsday viruses . Chase does not have time for Douglas' backup plan, so he relies on Leo to finish the job . Chase starts to explain what Leo should do, until everyone dies . Douglas returns to synchronize his laptop's firewall to the virus, but he instead follows Chase's plan and saves everyone . Everyone is virus - free, and Leo and S - 1 decide to let bygones be bygones . </P> <P> Guest stars: Jeremy Kent Jackson as Douglas, Ashley Argota as S - 1 </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 82 </Th> <Td> 14 </Td> <Td> "Bob Zombie" </Td> <Td> Guy Distad </Td> <Td> Hayes Jackson </Td> <Td> September 30, 2015 (2015 - 09 - 30) </Td> <Td> 417 </Td> <Td> 0.46 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Douglas creates a device that makes any bionic human as smart as Chase . After Douglas tests it on Bob, Bob starts spending time with Chase . This leaves Adam in envy . Meanwhile, Perry made the island officially her own, which makes Bree and Leo angry at her . </P> <P> Guest stars: Maile Flanagan as Perry, Jeremy Kent Jackson as Douglas, Brandon Salgado - Telis as Bob </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 83 </Th> <Td> 15 </Td> <Td> "Human Eddy" </Td> <Td> Victor Gonzalez </Td> <Td> Greg Schaffer </Td> <Td> October 14, 2015 (2015 - 10 - 14) </Td> <Td> 419 </Td> <Td> 0.38 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Donald gives Eddy a human body and replaces his disrespectful personality to make him nicer . Perry restores his old personality, and he attempts to harm the students . </P> <P> Special guest star: Will Forte as Eddy </P> Guest stars: Maile Flanagan as Perry, John Eric Bentley as President </Td> </Tr> <Tr> <Th> 84 </Th> <Td> 16 </Td> <Td> "The Curse of the Screaming Skull" </Td> <Td> Victor Gonzalez </Td> <Td> Loni Steele Sosthand </Td> <Td> October 21, 2015 (2015 - 10 - 21) </Td> <Td> 420 </Td> <Td> 0.50 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Leo just finishes his movie marathon while everyone else is frustrated because they have nothing to do on Halloween . Bob intentionally stays behind while the other students are away with Davenport to a museum . Perry says she's going to another island across from theirs, but Douglas says no because it's deserted and has been uninhabited for years . When Douglas leaves, the group decides to go anyway . While on the deserted island they come across a metal skull . Perry wants to bring with her to the academy, but Chase and Bree refuse to have it there and tells Perry to put it back . When everyone leaves, Perry sneaks the skull back to the academy . Meanwhile at the academy Adam teaches Bob about the art of Halloween but fails when Bob tells the others that Adam is trying to scare them with a skeleton . Perry paints the skull black and tries to sell it online . Leo, Bree, and Chase see this and Leo is immediately afraid saying everyone is cursed . Chase decides to take the skull back to the island despite Leo's paranoia . Bob tries to understand Halloween by showing Adam his most terrifying items such as a math test, a potato with eyes, and Santa Claus, but Adam is unimpressed . Perry runs into Bree and Leo saying that something is wrong . While trying to figure out what, a ceiling fan crashes down nearly killing them . Bree tries calm everyone down until a knives shoot across the room directly at Leo until he blocks it and a fireball hits Perry in the back of head, barely grazing her hair . Everyone is convinced that the skull is cursed and tells Bob and Adam, until Bob tells that everything was caused by Chase (with his skin turning pale and his eyes red). Bree decides to take it back to the island herself . Douglas arrives and tells him that skull is just a paperweight and virus was spilled on it and turns anyone evil for those who came into contact with it . Perry was uninfected when she touched it earlier because of the gloves she was wearing . Douglas decides to destroy it but can't because Bree left with it, and everyone sets out to find her, until she enters in the same condition as Chase . Bob is tied up when everyone returns, and Douglas uses Davenport's nanobots in the shape of an injector to cure Chase and Bree . Bree and Chase attempt to destroy everyone until Adam pretends to be infected to get close enough to cure Bree and Chase . With everyone cured, Douglas finally attempts to rebury the skull until Bob and Adam touch the skull . </P> <P> Guest stars: Maile Flanagan as Perry, Jeremy Kent Jackson as Douglas, Brandon Salgado - Telis as Bob </P> Absent: Hal Sparks as Donald Davenport </Td> </Tr> <Tr> <Th> 85 </Th> <Td> 17 </Td> <Td> "Lab Rats: On the Edge" </Td> <Td> Victor Gonzales </Td> <Td> Hayes Jackson Greg Schaffer </Td> <Td> November 11, 2015 (2015 - 11 - 11) </Td> <Td> 421 </Td> <Td> N / A </Td> </Tr> <Tr> <Td_colspan="8"> <P> Donald tells the group that the president has decided to host an award ceremony because they have completed their one - thousandth mission and Leo wants his recognition, but it's only for the original members . Disappointed, Leo forms his own team with S - 1, who calls herself Taylor now, and Logan . He shows the other Lab Rats that he and Taylor can fuse their abilities and can take out any power source, Chase demands they stop, but Leo pushes on . The blast becomes too much for Taylor and it incapacitates her . Leo feels completely guilty for what he's done and decides to quit the academy and go back to Mission Creek to live with his mom . Meanwhile, Donald builds a limo to be indestructible, but Douglas easily destroys it . Taylor regains consciousness and will be okay, but because of the blast it renders her permanently blind . Douglas invents a gadget that allows Taylor to echo - locate to detect obstacles in her way . Elsewhere, Adam and Douglas successfully make Davenport's limo completely indestructible . The family is on their way to the ceremony when the bridge begins to collapse, nearly sending the limo over the edge . The group becomes trapped as the limo locks down due to how it was built for emergencies . The students at the academy see them on the news and attempt to save them and the rest of the civilians still on the bridge . Taylor and Logan call Leo and ask him to help . They rush to the scene and manage to save everyone, but the limo is still sliding off the edge . Taylor, Leo, and Logan attempt to hit the fin of the limo so the lock down can be lifted and the others can escape . Bree opens the sunroof and uses her super speed to get the others out . She manages to get everyone except Chase, so Leo forces everyone off the bridge to so he can help him . Eventually, Leo manages to save Chase . Later at the academy, Donald decides to make Leo a mentor because he had proven to be a leader . </P> Guest stars: Jeremy Kent Jackson as Douglas, Ashley Argota as Taylor, John Eric Bentley as President, Emery Kelly as Logan </Td> </Tr> <Tr> <Th> 86 </Th> <Td> 18 </Td> <Td> "Ultimate Tailgate Challenge" </Td> <Td> Guy Distad </Td> <Td> Greg Schaffer </Td> <Td> December 2, 2015 (2015 - 12 - 02) </Td> <Td> 413 </Td> <Td> 0.40 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Tasha arrives on the Bionic Island informing everyone that she has tickets to a big football game of the Pioneers (mascot of a college that she went to) vs Vikings (mascot of a college that Perry went to) and Perry arrives stating that she has been trying to score tickets for weeks but it was sold out . When she asks Tasha if she has any tickets, Tasha lies saying that she hasn't . When they are about to enter the game, Perry eventually finds out the truth, she becomes furious and destroys the tickets which causes Leo, Donald, and Tasha to try to get new tickets competing against her in The Ultimate Tailgate Challenge, hosted by NFL former linebacker Willie McGinest . Meanwhile, Bree attempts to achieve her college experience by fitting in with a couple of college students (who are football fans) and attempting to use her bionics to impress them . But when Chase tells her not because it is too rational and embarrassing, he does it himself anyway, which causes her to become angry and jealous . Adam and Bob on the other hand stay on the island and create a web show about breaking stuff, but they accidentally destroy the capsules while playing disk with a coffee table, they eventually fix it but are busted . </P> Guest stars: Angel Parker as Tasha, Maile Flanagan as Perry, Brandon Salgado - Telis as Bob, Willie McGinest as Willie McGinest </Td> </Tr> <Tr> <Th> 87 </Th> <Td> 19 </Td> <Td> "And Then There Were Four" </Td> <Td> Victor Gonzalez </Td> <Td> Ken Blankstein </Td> <Td> January 13, 2016 (2016 - 01 - 13) </Td> <Td> 418 </Td> <Td> 0.41 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Everyone is shocked when Douglas introduces a fourth bionic sibling named Daniel who's been living a normal life with an adopted family . Daniel later comes to the academy to meet his father, uncle, and cousins . After Daniel's bionics are accidentally activated by the Lab Rats, Donald and Douglas find out what happened they have to come clean to Daniel about his power - replicating abilities . Daniel also finds out that his cousins are actually his biologic siblings . Filled with anger, Daniel goes out for air on the beach, where Leo and him have a conversation about Douglas . Not too long after, Daniel, using Leo's abilities, accidentally causes a leak in the hydro - loop's fuel tank . After Adam and Daniel combined their powers to stop it, Douglas apologizes to Daniel for lying and Daniel decides to give Douglas a second chance . </P> Guest stars: Jeremy Kent Jackson as Douglas, Pearce Joza as Daniel </Td> </Tr> <Tr> <Th> 88 </Th> <Td> 20 </Td> <Td> "Space Colony" </Td> <Td> Victor Gonzalez </Td> <Td> Chris Peterson Bryan Moore </Td> <Td> January 20, 2016 (2016 - 01 - 20) </Td> <Td> 424 </Td> <Td> 0.64 </Td> </Tr> <Tr> <Td_colspan="8"> <P> In the middle of a massive heat wave, the whole family is going to space to see Donald's space colony, called "Davenportia". Adam annoys Chase while Chase tries to give his safety instructions and accidentally blasts them into space . After leaving the solar system, they initiate hyper - speed and land on the planet Lithios . In the dome, it's discovered that Perry sneaked her way in with the rest of the colonists . In the command center, one of the satellites loses contact with Earth and the Lab Rats try to fix it . Leo and Donald find a punctured hole in the dome, releasing the oxygen within . Chase checks out the satellite, but can't seem to find anything wrong with it . He detects that it's someone tampering with the system back on Davenportia . As Chase heads back to the ship, his jet pack malfunctions and drifts him off into space . Unable to reach him due to range, Perry plans to fly the ship to find Chase . Leo and Donald use their jet packs to seal the hole in the dome . On a deserted planet, they find Chase unharmed because of his force field . On the ship, Chase vows not to speak to Adam because of his reckless actions . Donald is nearly pulled out into space, but Leo pulls him back and patches the hole . When the Lab Rats and Perry come back, they find everyone missing . A person in a suit comes out and reveals himself as Krane and says everything was caused by him . He has come back to create a new army of bionic warriors with his new partner, Dr. Gao . He attacks Chase and implants the Triton App in Donald . Gao gives himself bionics and plans to give everyone liquid bionics . Leo gets his fire blaster to shoot the bins of liquid bionics and Bree takes off Krane's oxygen tube . Gao escapes and Leo shoots the hole in the dome as everyone is escaping . On planning a way back to Earth, Gao enters the ship and implants Leo with the Triton App while covering his mouth to prevent him from calling for help . Leo attacks the group and is subdued by Adam and Bree . Gao explains that he will wipe out all human existence on Earth with a doomsday missile . Leo attacks again, but Bree tries to distract him by turning invisible . Leo then hits Gao, knocking him out, and Perry locks them up . Krane manages to survive and begins to attack the ship from one of the colonists' space pods . Krane takes out their defense mechanism and their homing device . Chase manages to lock on to Krane with the missile and destroys him . However, the other missile is still heading toward Earth and Chase decides to use Donald's high velocity escape suit, but Bree tells him he'll die because of the force it has . Adam decides to do it instead because his strength will help his chances of surviving . Chase thinks it too risky, but Adam is willing to take the risk in order to save the world . After a while he becomes unresponsive due to blacking out . When he comes to, Adam destroys the rocket . </P> Guest stars: Maile Flanagan as Perry, Angel Parker as Tasha, Graham Shiels as Krane, Ping Wu as Dr. Gao </Td> </Tr> <Tr> <Th> 89 </Th> <Td> 21 </Td> <Td> "The Vanishing" (Part 1) </Td> <Td> Victor Gonzalez </Td> <Td> Hayes Jackson Greg Schaffer </Td> <Td> February 3, 2016 (2016 - 02 - 03) </Td> <Td> 423 </Td> <Td> 0.68 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Donald and Douglas reveal that they have built an upgrade for all the students' bionics, except for Leo's . But the upgrade doesn't work on Adam, Bree, and Chase because their systems are older . Adam, Bree, and Chase are therefore left at their level, while all the students are much more powerful . Meanwhile, Daniel is brought to the Academy because he had been using his bionics in the outside world . Douglas decides to enroll Daniel at the Academy, and he makes Leo his mentor . Leo steadily tries to teach Daniel, but Daniel proves to be unteachable, so Leo gives him the upgrade as well . The students steadily start to vanish, including Daniel . Giselle Vickers, Douglas' old girlfriend, is revealed to have captured them . Daniel sends a video message to the Island, requesting help . Donald, Douglas, Adam, Bree, Chase, and Leo suit up and go to Giselle's lab . There, Daniel draws them into a room that immediately locks itself . Giselle comes out, and shows them that the students are trapped in another room, including Daniel . Then the Daniel that drew them into the room reveals himself to be Marcus . </P> Guest stars: Jeremy Kent Jackson as Douglas, Mateus Ward as Marcus, Brandon Salgado - Telis as Bob, Jessalyn Wanlim as Giselle, Pearce Joza as Daniel </Td> </Tr> <Tr> <Th> 90 </Th> <Td> 22 </Td> <Td> "The Vanishing" (Part 2) </Td> <Td> Victor Gonzalez </Td> <Td> Chris Peterson Bryan Moore </Td> <Td> February 3, 2016 (2016 - 02 - 03) </Td> <Td> 423 </Td> <Td> 0.71 </Td> </Tr> <Tr> <Td_colspan="8"> <P> Giselle reveals she dug up Marcus from Douglas' old lair and rebuilt him, piece - by - piece . Marcus wants revenge on Douglas for leaving him to die . Everyone rushes Giselle and Marcus, but Marcus knocks everyone unconscious . Donald and Douglas are tied together in chairs, while Adam, Bree, Chase, and Leo are put in the chamber with the students, while Daniel is pulled out . Giselle burns out the Lab Rats and the students chips but doesn't tell them . Leo is the only one who can use his bionics, so he frees everyone from the chamber . Giselle leaves to stop them, but the Lab Rats let the students escape and they fight Giselle alone . Giselle attempts to use her whip to destroy Adam, Bree, and Chase, but her attack misses, causing the whip to tie around herself, cutting her in pieces . Meanwhile, Marcus tortures Daniel in front of Donald and Douglas, and after failed attempts to turn Marcus to their side, Douglas reveals that Daniel can replicate Marcus' bionics . Daniel uses this ability to blow Marcus up . After everyone regroups, Donald tells the Lab Rats that in order to repair their bionics, they would have to go back to the old lab in Mission Creek . Once there, Donald and Douglas reveal that they created one universal bionic super chip, so they would all get the upgrade . Douglas also reveals that he brought Marcus' parts from Giselle's lab, and he expresses his desire to rebuild Marcus and reprogram him to be good . Everyone else disagrees . Tasha comes down and reveals that she is pregnant with a girl . Perry comes and reveals her relief that everyone's okay . Everyone but Leo goes upstairs to eat, and Leo throws Marcus' parts on the ground . As Leo is walking away, Marcus' regenerates . Leo and Marcus stand off, and before either of them can attack, Douglas blasts Marcus, melting him . Later, as the Lab Rats are packing to go back to the Academy, Donald walks in and tells them that he's splitting them up . It is decided that Adam and Leo would go back to the Academy, while Bree and Chase would stay with Donald to work on a mysterious new project, with a mysterious new team . When Adam and Leo leave, Donald asks Bree and Chase, "Are you ready to start your new adventure?" </P> Guest stars: Maile Flanagan as Perry, Angel Parker as Tasha, Jeremy Kent Jackson as Douglas, Mateus Ward as Marcus, Brandon Salgado - Telis as Bob, Jessalyn Wanlim as Giselle, Pearce Joza as Daniel </Td> </Tr> </Table> <Tr> <Th> No . overall </Th> <Th> No. in season </Th> <Th> Title </Th> <Th> Directed by </Th> <Th> Written by </Th> <Th> Original air date </Th> <Th> Prod . code </Th> <Th> U.S. viewers (millions) </Th> </Tr>

What happens in the last episode of lab rats
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