Ruthless People (1986) - 3 mistakes

Continuity: When Judge Reinhold is in his kitchen with Helen Slater he tells her they have to be ruthless. He sees a spider on the floor and gets a magazine and scoops it up. Then he goes outside to let the spider out and he puts the magazine down for 1/2 of a second. He was supposed to put the spider on the ground but if you look nothing comes off the magazine. Then he goes to squash it with his foot, but what can he squash if there's nothing there?

Factual error: Barbara befriends her kidnappers in her joy over losing 20 pounds while she was with them. Leaving aside that she's been with them no more than two weeks, and it's near impossible to lose 20 pounds in that short amount of time even if you literally starved yourself; she also most definitely would have noticed a weight loss that big. On a frame as small as hers, she would have noticed big differences in her body's shape and feel, and none of her clothes would have fit.

Revealing: When Danny DeVito brings home the 'bigger dog' he says for the new dog to go eat the little dog that always bothers him. He lets the dog go and the dog goes after the little one. But when they show the dog chasing the little one he almost runs right past him. There must have been a trainer on the other side of the set calling the dogs to come over because he wasn't chasing the little dog.