Continuity mistake: During the scene where Dottie and Jimmy are sitting beside each other at the front of the bus having a conversation, the camera cuts to Mae painting Kit's nails on the back seat of the bus. When the camera cuts back to Dottie and Jimmy, if you look at the back seat of the bus, Mae is sitting by herself and Kit is already about to sit back down in her seat in the middle of the bus. It doesn't seem likely that there would have been enough time for her to be in that position so quickly.
Continuity mistake: During the tryout/league formation sequence at Harvey (Wrigley) Field, every shot takes place at the famous stadium, except one. When Betty Spaghetti backpedals to catch a fly ball, the background shows a rickety wooden outfield fence, not Wrigley's famous ivy-covered walls.