(at around 16 mins) When Little Nicky exits Grand Central Terminal and spooks the street preacher, the traffic on the street disappears and reappears.
(at around 46 mins) After Nicky gets sprayed with mace on the fire escape outside Valerie's bedroom, he stumbles backward and begins to fall over the railing. In the next shot, however, his body is falling forward over the railing.
(at around 51 mins) When the mob is chasing Little Nicky, his parting changes briefly from his left side to the right side.
(at around 3 mins) At the very beginning when Nicky is "air jamming" to Van Halen's "Runnin' With The Devil" (which is playing on the right turntable), the turntables have no covers up until just before Jimmy The Demon walks in, then they are covered after that.
When Nicky is playing basketball against Cassius, and Nicky has the ball, when the picture shoots in to Cassius, he appears to be holding a basketball as well, although when the shot cuts back to both of them in the picture, Cassius isn't. Then, when the shot goes back in to Cassius, he's holding the basketball again.
(at around 41 mins) Nicky holds the jacket from the Chicago V album. The song he plays ("Does Anybody Really Know What Time It Is") is from Chicago's first album called Chicago Transit Authority (or Chicago I).
(at around 1h 10 mins) The "rabbit" that demon bites and rips the ear off is clearly a stuffed toy.
(at around 21 mins) When Adrian is possessing the Cardinal, the possessed cardinal is standing barefoot on a steaming hot pizza. It's hard to believe that no one in the church would notice the steaming hot pizza, but it's even harder to believe that no one in the church would notice the possessed Mayor. He stood up in front of the crowd, with tin foil wrapped around his feet like shoes.
(at around 2 mins) When the Peeper is spying on the mother undress in the beginning, the son barges right into her room easily. Logically she should have locked her door.