Revealing mistake: When Carl is being dragged away by the demons, you can see the cable line that he's attached to. May be fixed on DVD.
Plot hole: At the end of the film, we see Edward carving ice sculptures in his mansion. How did he get the ice up there? First of all, it takes place in a warm climate and I didn't see a freezer up there in the castle. He couldn't have gotten ice from town because firstly he had scissors for hands and couldn't have gripped the ice. And, even if by some miracle he could, he wouldn't be able to buy any from town because everyone in town but Kim was convinced that Edward was dead, she told everyone that they killed each other. And Kim didn't bring it to him because she told her granddaughter in the end that she never saw him again after that night. So where did he get that ice?
Continuity mistake: When Molly takes Mikey into work and he is under the desk, Rona is still wearing her shoe. Yet when the scene changes, her shoe is missing when Mikey starts tickling her foot. Then when the boss realises that Mikey is under the desk, her shoe is back on. When the shot changes again, her shoe is off.
Factual error: Cher complains that Astroturf is going to ruin baseball. Mermaids is set in 1963 when Astroturf was still being developed under the name Chemigrass. It wasn't christened Astroturf until it made its world debut on the floor of the Houston Astrodome in 1966.
Continuity mistake: When the Drapes are singing to Allison/Baldwin/Mrs. Vernon Williams, the song, "Gee, I Love that Girl" in the speeding cars, Hatchet-Face's gold earrings are on, then off, then on again. They are seen again in other scenes.
Continuity mistake: At the end of the movie, Jack parks the car in front of a palm tree and walks onto the beach. The shot changes while he stands there for a few minutes. As the shot changes back to show him walking off the beach, the car is no longer in front of the tree, nor does he drive by during the credits. I hope he enjoys his walk back to Miami.
Continuity mistake: When Harry Maddox is about to go for a ride with Dolly Harshaw, he reaches for his shirt and is mesmerized by the legs of his other love interest, Gloria Harper. Gloria catches Harry admiring her, with her head turned backwards, cigarette poised near her lips. In the frames immediately preceding this moment, she clearly does not have a cigarette, lit or unlit, anywhere near her.
Continuity mistake: When Baldwin kills the guy in the barber shop, he uses a Desert Eagle, a semi automatic pistol, yet it never ejects any shells.
Continuity mistake: Sailor Ripley and Bobby Peru are robbing the Feed Store in Texas. Bobby says "Say cheese" shooting one of the two men. We can see that his right hand is blown off. Cut to a shot of the two men searching for the hand and the victim has a bloody left stump. Then the store dog runs out with a right hand in its mouth.
Plot hole: Georges repeatedly tells immigration officers about his Africa trips. This overlooks that fact that INS would have or request a copy of his passport to process his case. In real life, INS would have realised immediately that the Africa story was not real: no entry/departure stamps in his passport.