Continuity mistake: During the various ski scenes, the weather changes frequently between shots - in some shots, the sky is clear and harsh shadows are cast. In other shots, it is heavily overcast and shadows are barely visible.
Continuity mistake: In the final skiing scene, the skiers have different skis on from shot to shot. I have counted a total of four pairs of skis on Lane alone. Obviously that is not John Cusack doing the skiing either.
Factual error: Lane and Monique are side by side under the Camaro, when Lane loosens a bolt (or nut) which results in oil pouring over his face. On the right side of the engine, there is no plug which when loosened would result in oil leakage.
Continuity mistake: In the dining room scene when they are having dinner with Monique, the liquor is red. When Ricke's mom pours it, it's changed to clear.
Continuity mistake: When the kid shows up asking for 2 dollars he has a hat on. A second later miraculously he whips out a comb and starts combing his hair.
Answer: It was an idiotic diet fad in the mid to late eighties.