Continuity mistake: When Nick is singing "Spend This Night with Me", he brings up a girl from the audience. Watch the background. When it shows another girl from the audience, in the next shot, you can see a speaker that wasn't there before. Moreover, when he picks the girl, we can see that there isn't anyone at her left side. But a few seconds earlier she was sitting between two girls (the one at her left was wearing a white shirt). (00:42:05)
Revealing mistake: When Supergirl flies through the window to fight the invisible monster, half of the screen shows her jumping in a school uniform and the other half exiting with the Supergirl outfit. Watch closely and you'll notice that her halves don't match, giving the sense that she is missing part of her body.
Visible crew/equipment: When a gremlin attacks the Mum from a Christmas tree, and the tree falls on top of her, you can clearly see a member of the crew with eyeglasses, wearing a red shirt, standing behind the tree pushing it forward on top of her. (00:54:30)
Continuity mistake: When the eggs pop out of her bag and start cooking on the counter, they're in different positions depending on whether it's a close up or wide shot. (00:18:55)
Continuity mistake: During the first chase scene, the semi passes by an empty taxi cab and when the camera angle changes, the semi crashes into the same taxi cab. (00:06:05)
Continuity mistake: When the Rad Pack first meets and are skiing together, Dan O'Callahan is wearing a blue baseball cap and sunglasses. In some later shots he is wearing a stocking cap and goggles. (00:31:25 - 00:32:00)
Revealing mistake: When Hanks drives through the city escaping form the MPs, the guy driving is a very obvious stuntman.
Continuity mistake: The dodge truck that gets blown up on the county farm is not the same as the one the deputies are driving. The "Dodge" emblem is missing and the mud pattern is different. (01:09:40)
Continuity mistake: The first car he jacks is a white 4 door Oldsmobile Cutlass salon, and a 2 door Olds Cutlass Supreme in the next. (00:09:30)
Continuity mistake: When Elaine gets knocked out with the ball her hat falls to the ground, next to her car. When the boy drives off the hat is gone. (00:12:55)
Continuity mistake: When Jackie jumps off his balcony the first morning, the Spanish grocer is ducking with his hands above his head, while in the close-up of Jackie landing he's using his hands to shield his veggies. (00:04:00)
Continuity mistake: At the start of the film, Mahoney is wearing a white shirt with badges on it from the company he works for. When he's being interrogated by Sgt. Reed the shirt remains the same until the last part of the scene. The camera stays on Mahoney and we can see that the badges on the shirt are gone. If you look closely, you will notice that he is even wearing a completely different white shirt, which now looks more scruffy and creased. (00:08:00)