Revealing mistake: During the montage when Torrance is talking about how they are going to have to practice longer and harder they show the squad attempting to do a Wolf Wall again. But you can tell that it is the same scene as the beginning, because all the people are wearing the same clothes and you can even see Carver, the girl who broke her leg, standing there next to Torrance. (01:01:04)
Revealing mistake: When Sparky teaches them the routine, he gets mad, picks up a stool, and smashes it on the floor. You can see (at the bottom of the screen) the top fly off the stool before it touches the ground, which shows that it wasn't glued or screwed together in the first place.