About half an hour in to "Robin Hood: Men in Tights," Maid Marian's nanny of sorts (Broomhilde) tells Marian to get out of the tub before her chastity belt rusts. At the end of the movie, Robin's key FITS in the lock, but the mechanism won't work. Guess she was in there a little too long...
Rottingham's jackhammer can't have helped matters, either.
The assassin sent by Don Giovanni perches in a "Folio Depository" — but you might not catch the reference to Lee Harvey Oswald and the assassination of John F. Kennedy unless you know that a "folio" is a type of book.
Fridge Horror: Some of the prisoners that escaped in the beginning must have been there for a legitimate reason, like murder.