Frankie Muniz does an excellent job making himself look like a kid who has told "one too many" lies, and now suffers "cry wolf" syndrome.
After Jason Shepherd notices a Hollywood director (he had an accident with) has stolen his English paper and turned it into a successful movie script, he (played by Muniz) sets out on a hilarious adventure to get credit for his work. The best part about the movie is I truly believe something like this has probably happened before...only the person with the stolen screenplay probably did not have the brain power of Muniz and Bynes!
The movie is good clean fun for the whole family. Amanda Bynes knows how to play to the camera, as does just about everyone involved with this movie. Paul Giamatti's "Hungry Like The Wolf Dance" as a blue-colored moron was one of the funniest scenes in a PG movie in a while.
Buy it, watch it, laugh...
P.S. If you go to the video store and it is a choice between Big Fat Liar or Lost In Translation, trust me - go with Big Fat Liar.