Corrected entry: While the mouse is listening to "Baby Mine," watch his eyes. During one shot, I think it's the first one of him swaying back and forth and smiling, the white around his pupils suddenly turns to gray.
Corrected entry: In the scene where the ringmaster is explaining his new idea for a performance to the janitor, he mentions "until finally all seventeen elephants have constructed an enormous pyramid", but in the elephant pyramid scene there is only 7-8 elephants.
Correction: The remaining elephants would have to be trained, yet. They won't instantly know how to do it, and can't all be trained at once.
Correction: Just watched this and his eyes remain white throughout the entire scene.
THGhost