Continuity: When he has the accident after hitting the dog, there is a big very noticeable dent in his truck. After he leaves the camp place it is gone and never seen again.
Great sites
Mistakes
When John returns from the hospital, Maya is sitting down, then stands up. The camera then goes onto John, then back to Maya, then she stands up again. See more...
Dr. Dolittle mistakes
Factual error: Dr. Dolittle is driving through San Francisco with a cup of Dunkin' Donuts coffee - there are no Dunkin' Donuts in San Francisco.
Deliberate "mistake": In the scene where Maya is looking for Rodney at the party and he scampers off into the bathroom, he miraculously climbs on top of a toilet in a matter of seconds (which isn't actually shown). There is no way a guinea pig could do this.
Dr. Dolittle trivia
The scene where Dr Dolittle awakes to find the guinea pig in the bed with him looks like an homage to the horse's head scene in The Godfather. The way he screams, and the way the camera cuts to an external shot, is an exact copy.
Eddie Murphy had a big problem while working on this movie: He is very squeamish about most animals. It is even so serious that he flatly refused to do a scene involving an alligator. Hence, most shots with animals were done via blue-screen technique.