Continuity mistake: Billy has a magic baseball uniform - at the end of the movie, he steals home again, sliding face first into the plate on his stomach. Yet when he's walking off the field with Robin and Appleby, there are no dirt marks on his uniform.
Continuity mistake: We see Billy and Katie laying in beach chairs on the deck. In the frontal perspective, the end of Katie's blue hair ribbon is resting on her chest. Cut to a side view, and the ribbon is suddenly on her shoulder.