Continuity mistake: In the scene where Wyatt and Gary are taking Deb and Hilly home in the Ferrari and Porsche, Gary is being pursued by the police. When Gary approaches the railroad tracks, the train is shown coming in the direction of the passenger side door. When they finally cross over the tracks, the shot is flipped, and the train is seen to have crossed the intersection in the direction of the driver's side door.
Continuity mistake: There aren't any shoes on the Lisa doll, but the real life Lisa appears wearing high heels.
Continuity mistake: Lisa is trying to convince Gary's parents to let him go to the party. There is a glass of beer on the table. The camera switches to a close up and then back to a wide shot and the beer is gone.
Continuity mistake: When the ritual candles are first seen, one of them sits in a white corner area of the Life boxtop. In a later shot the candle moves in and sits on (newly appearing) black text.
Continuity mistake: Lisa has just exited the shopping mall. Gary pulls up in the Porsche. When Gary pulls up onto the curb, the cars behind the Porsche include A white coupe, a blue sedan, a silver Chevy Monza and a brown Lincoln Town Car. Gary gets out of the Porsche and says " Lis' we're running late" and the cars have completely changed except the silver Chevy Monza. Lisa turns to get into the Porsche and the cars behind them have completely changed yet again. Now they include a Brown Van and a silver 4 door Plymouth Horizon. Obviously the mall parking lot was not closed during filming, and this 2 minute scene was shot over the course of several hours.
Revealing mistake: Arriving home from his hunting trip, Chet Donelly (Bill Paxton) finds Gary in bed with a girl. Chet whacks them both over the head with his rifle and you can clearly see the barrel bend with each hit.
Continuity mistake: When Chet and Wyatt are in the kitchen getting breakfast, the paper towels in the background are all rolled up. From the point when Chet says, "That's not a joke," a loose paper towel is hanging down from the roll.
Continuity mistake: In the scene where Max dumps the slushee, the cup was filled way over the top with slushee. When he turns the cup to dump it, the slushee is now down way below the top of the cup.