<P> Lawrence Fletcher (voiced by Richard O'Brien) is the father of Ferb and stepfather of Phineas and Candace . Lawrence sells antiques, is from the United Kingdom and is portrayed like a sitcom dad as being scatterbrained and unaware of what is going on . He often agrees to follow Phineas's instructions and even forces Candace to cooperate as if he considers Phineas and Ferb's skills normal . Unlike the boys' mother, he has seen some of the boys' inventions; he has not reacted negatively, and apparently believes that their mother approves . His precise surname is a matter of some dispute; in at least one episode, Isabella addresses him as "Mr. Flynn". Jeff "Swampy" Marsh has said that Lawrence Fletcher is very similar to his stepfather, Bill . </P> <P> Linda Flynn - Fletcher (voiced by Caroline Rhea) is the mother of Phineas and Candace and stepmother of Ferb . Unaware of the large - scale projects that Phineas and Ferb create on a daily basis, Candace often drags her away from other interests in an attempt to get the boys in trouble . Each creation is somehow destroyed or eliminated moments before "Mom" arrives leaving Candace dumbfounded and Linda once more reluctant to believe Candace the next time . She was also a one - hit wonder known as "Lindana" with her song, "I'm Lindana and I Wanna Have Fun". That fact possibly makes her, as a singer, a parody of Cyndi Lauper, because of Lauper's hit Girls Just Want to Have Fun, and because both of them were famous singers in the 1980s (Linda fictionally). Her single is used as elevator music throughout the series . Her surname is not consistent throughout the series; in at least one episode, Candace refers to her as "Linda Flynn". She is based on Dan Povenmire's sister, also named Linda . She also used to date Dr. Doofenshmirtz during their mid-teens and that she was the one who inspired him to take over the Tri-State Area as a starting point for worldwide domination when he sarcastically stated that he would rule the world . </P> <P> Isabella Garcia - Shapiro (voiced by Alyson Stoner) is a Jewish Mexican girl . She is one of the brothers' best friends and has an obvious crush on Phineas Flynn of which he is unaware, though he has shown he cares for her from time to time . She is known for the catchphrase, "Whatcha doin'?" and is the leader of the Fireside Girls troop 46231 . The troop often helps Phineas and Ferb in their projects . She is named after series creator Dan Povenmire's oldest daughter . </P> <P> Stacy Hirano (voiced by Kelly Hu) is Candace's best friend . She is of Japanese heritage . Stacy is shown to be annoyed by Candace's constant attempts to bust Phineas and Ferb, and would prefer to just have fun with the inventions; she also occasionally gets annoyed with Candace's gushing about her relationship with Jeremy . During the episode "Happy Birthday, Isabella", she finds out about Perry's secret Identity but doesn't lose her memories afterwards . </P>

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