7. The CrissCross Puzzle Company - Batman Forever
Despite the fact that Joel Schumacher basically destroyed Bane and Mr Freeze with madcap character reboots, and reimagined Two Face as a sub-Joker charlatan - ignoring the majority of the source material for all of the villains in the process - he did manage to shoe-horn in a blink-and-you'd-miss-it reference to the Joker in the original comics. In the background of one shot, there's a sign for the CrissCross Puzzle Company, which was of course the chosen method of transmission of his riddles, and of his first clue way back in the 1940s. It's a smart reference that only the most ardent of Riddler fans would probably understand.