A take on the classic tale 'The Boy Who Cried Wolf', 'Big Fat Liar' is about a 14-year-old boy named Jason Shephard (Frankie Muniz) who lies for the fun of it. Jason loses an important story assignment entitled 'Big Fat Liar' in movie producer Marty Wolf's (Paul Giamatti) limo, which Wolf then turns into a film. When Jason sees a movie preview of his story, he and best friend Kaylee (Amanda Bynes) go to Los Angeles to make Wolf confess to using Jason's story as well as to clear Jason's name and to get him out of having to attend summer school. The teen liar then has to match wits with Wolf, who also turns out to be a big liar.