9. The Joker's Mask Is An Homage To The 1960s TV Series - The Dark Knight
The bank heist opening to Christopher Nolan's The Dark Knight is absolutely unforgettable, but no matter how many times you've seen it, you probably missed a killer reference hiding in plain sight.
The Joker (Heath Ledger) and his fellow thieves wear distinctive clown masks throughout the heist, though the Clown Prince of Crime's own mask holds a very special significance.
The pattern - a blue beard, red eyes, and blue curved eyebrows - is actually a secret homage to an episode of the 1960s Batman TV series.
The first-season episode "The Joker Is Wild" marks the debut of The Joker (Cesar Romero), who later in the episode masquerades under a clown mask while performing the opera "Pagliacci."
His mask looks almost identical to that worn by Ledger's Joker over 40 years later, and given that it marks the actors' respective debuts as the character, it's a fantastically poetic tipping of the hat.