<Li> Jennifer Connelly as Helen Benson, a astrobiologist at Princeton University who is recruited by the government to study Klaatu . Connelly was Derrickson's first choice for the part . She is a fan of the original film and felt Patricia Neal's original portrayal of Helen was "fabulous," but trusted the filmmakers with their reinterpretation of the story and of Helen, who was a secretary in the original . Connelly emphasized that Helen is amazed when she meets Klaatu, as she never believed she would encounter a sentient alien like him after speculating on extraterrestrial life for so long . Connelly was dedicated to understanding her scientific jargon, with Seth Shostak stating she did "everything short of writing a NASA grant application ." </Li> <Li> Jaden Smith as Jacob Benson, Helen's eight - year old stepson . Jacob replaces the character of Bobby (Billy Gray) in the original, and his relationship with Helen was written as a microcosm of how Klaatu comes to see humanity--the alien sees their cold and distant relationship as normal human behavior, and their reconciliation forces him to change his mind . Smith said he found Jacob difficult to play because he felt the character "opposite" to his personality . Smith had met Reeves before on the set of The Matrix sequels, which featured his mother Jada Pinkett - Smith . </Li> <Li> John Cleese as Professor Karl Barnhardt, a Nobel Prize - winning physicist who specializes in the evolutionary basis of altruism . Helen takes Klaatu to him to further change his mind . The role was the most difficult to cast, and eventually the filmmakers decided to approach Cleese, noting "Who would you rather make the argument (to Klaatu) for mankind than John Cleese?" Stoff, a producer, had met Cleese a few times beforehand and had noted his intellect . The actor was surprised the filmmakers were interested in him, and decided playing a dramatic role would be easier than to play a comedic one at his age . He was often reminded to speed up his dialogue so that Reeves would not appear in synchronity with normal human speech patterns . Cleese said he is not interested in extraterrestrial life because he often philosophizes about the purpose of life and why humans are distracted by trivial matters . Cleese spoke about portraying abilities outside his own experience in the scene in which Klaatu corrects a complex mathematical formula Barnhardt has written on a blackboard: "The trouble is, I had to be able to write the equation, because Barnhardt has been working on it for 60 years . I learned to carefully copy things down that mean nothing to me at all . In A Fish Called Wanda, I spoke a lot of Russian without having any idea what it means ." The crew enjoyed working with Cleese and were sad when he finished filming his part . </Li> <Li> Jon Hamm as Dr. Michael Granier, a NASA official who recruits Helen into his scientific team investigating Klaatu . Granier is fascinated by Klaatu, but is torn between his official obligation to detain the alien and protect his country . Hamm acknowledged science fiction was a niche genre when the original film was made, and that it used science fiction to make topical issues more approachable . Hamm had the same feelings for this remake . Originally, Hamm's character was French and named Michel . Although he is interested in math and science, Hamm found his technical dialogue difficult and had to film his lines repeatedly . </Li>

What happens at the end of the day the earth stood still