Continuity mistake: In the beginning of the movie, Mavis stares at the window. When Drac sings to her, the window is closed in the first shot, but in the next shot it's opened. (00:01:00)
Plot hole: In Hotel Transylvania 2, at the end of the main characters' visit to Camp Winnepacaca, we learn that vampires cannot hypnotize other vampires, but in this movie, during the chase scene where Dracula attempts to restore Johnny to his human form, Dracula successfully hypnotizes Dennis to eliminate any witnesses. Since Dennis has been a vampire since the second movie, he should not have been able to be hypnotized. (00:21:30)
Continuity mistake: After Dracula wakes up from being unintentionally knocked out by Johnny, they find themselves at the top of a very high cliff. There are two shots featuring Dracula and Johnny with the entire cliff visible; in the second shot, as they are falling, Johnny and Dracula appear to have shrunk tremendously. (00:52:30 - 00:53:00)
