Factual error: There are a few things wrong with the swan egg that Maya has found. First, in the opening scene we see that the egg is a hard-shelled egg, and it appears much too large for a swan egg. Second, at the end of the film, the egg hatches to reveal a baby alligator. Alligator eggs are soft shelled. Third, alligators are not native to San Francisco, but the southeastern United States.
Continuity mistake: When Lucky the dog is in Dolittle's car, he says "Tree, tree, tree" and in doing so, puts his paw on the button and gets his head stuck in the window. At this point you can see there is nothing next to Lucky's head, but in the very next shot he has placed his left paw on the window.