When Johnny is on his date with Missy, his ear falls off at night time. Yet when he is in the doctor's office and has tests run, he says his ear fell off twenty minutes before, when it is clearly day light outside the office.
Johnny died by being shot in the middle of his chest, after Big Chuck and friends shoot Johnny he goes and changes his shirt. the cause of death hole is missing.
The Coke cup that Johnny brings back from the refreshment counter into the movie theater is obviously empty.
Johnny's skin color is turned pale by make-up, and in many scenes his real skin color is seen under the false color due the uneven make-up treatment.
When Johnny comes out of his grave and is talking with the groundskeeper, you can see Johnny's breath due to it being cold on the set. Later, in the doctor's office, he breathes on the mirror and... nothing.
Johnny's left ear falls off in Missy's mouth but when he goes to the doctor's office he turns his head slightly and for a brief moment you can see the ear that was supposed to have fallen off.
In the finals scene where Johnny and Missy finally have their dance, Buck is smiling, while he shouldn't, while he's watching the dance.