Continuity mistake: When Fink is explaining the difficulty of the boot on the chalk board, he draws one circle on the toe of the drawing, it then changes to two after he throws Bo Bo and says "Sorry" and changes back to one circle again. You can tell that they are two different drawings altogether.
Continuity mistake: The beer that the guys make from the stolen recipe is a reddish-brown color. When the Wolfhouse brothers begin to bottle and sell the beer, the beer is in light green bottles. The beer inside the bottle is not reddish-brown, or else the bottles would have looked darker when full. The unopened bottles look like there's a light-colored beer inside of them.
Continuity mistake: In the scene towards the end of the movie where the Americans are preparing to face the Germans in the all boot double or nothing challenge, when they are shot from the side there are 10 boots on the table. In the next shot when we see the American team face on, only the Americans' 5 boots are still on the table. Then when they go back to the side view in the next shot all 10 boots are back on the table.