Revealing mistake: When Richie says "Don't you dare call me overweight young man" and tips the ferris wheel cart over, you can see that it is a dummy representing Richie.
Revealing mistake: During a few of the "flaming fart" scenes, you can see a wire connected to the bottom of the actors. It's hard to see because it appears that it was attached to their legs in some way, but you can still see it when they move around a lot. The easiest place to see it is when the "devil" knocks on the door and they all fart and jump around, look carefully between/to the side of eddies legs for a black wire. It's not the dressing gown belt because that's tied around their waists.
