Continuity mistake: After Mortimer picks up Elaine and literally throws her out the front door, he locks it to make sure she doesn't just open the door and walk in again. When Aunt Abby goes to open the door for Mr. Gibbs less than a minute later, she doesn't have to unlock it.
Factual error: The movie opens on Halloween in Brooklyn. To show how crazy things were in Brooklyn, they show a baseball game being played by the Brooklyn Dodgers that day at Ebbetts Field and a big fight breaks out. The baseball season is and was over (including the World Series) well before Halloween. So there is no way they could be still playing on Oct 31st The only exception was in 2001 when games were postponed due to the 9/11 attacks and the season didn't end until November.