When Melissa is playing a game of Hangman with Mary on the high school blackboard, the two Ns on "Ghouls just want to have fun" are already filled out. When Mary loses the game and Melissa fills in the missing letters, she fills in the N on "want", despite the fact that both Ns were previously filled in and that the N in "fun" is still filled in.
After the Cadillac's roof is torn up by a zombie, it is seen sometimes intact, sometimes torn until the end.
At the end of the movie the DJ plays a request for Phil from Sandy that hadn't been recorded when she was alive - 1965's "Baby I'm Yours" (Sandy passed away in the 1950s.