Continuity mistake: In the beginning when Topper is about to fight, he puts a red bandana around his head. As he is walking to the fight, one of the flaps of the bandana is draped over his shoulder. The shot changes when he gets to the fight, and both flaps are now behind his shoulders.
Revealing mistake: When Topper is fighting the Thai Fighter, they break the ladder that sends some people falling down. Before the shot cuts, you can see the guy with the pink shirt falling, and he has a dummy attached to him. This is not the same as other dummies who are obviously meant to be noticed (like the guy holding the "John 3:17" sign).
Continuity mistake: When Topper is trying to get the keys to free the colonel, he knocks the pepper-shaker over, but there's no visible concentration of pepper. After the colonel gets the keys, a mouse is shown on the table. It goes up to the newspaper and sneezes from the mound of pepper which was not there before.