Since the very first Batman films of the 1940s, there have been many iconic portrayals of the Dark Knight and his legendary roster of allies and villains. Here are some facts from behind the scenes that even the biggest fans may not know about.

Many still say Michael Keaton gave us the best film version of Batman, but his casting wasn't always seen as great news. Thousands of fans sent letters to Warner Bros. to criticize the casting choice.

Photography: Warner Bros. Pictures

Heath Ledger's performance as the Joker in The Dark Knight included a lot of iconic little tics and traits, but one of them was born of necessity. He licked his lips because it helped keep his scar prosthetics in place.

Photography: Warner Bros. Pictures

When Jack Nicholson played the Joker in 1989, he agreed to $4 million less than his normal rate in exchange for a percentage of the film and merchandise profits. The "pay cut" ended up earning him about $90 million.

Photography: Warner Bros. Pictures

Batman's suit has evolved over the history of the movies. The one Michael Keaton wore in 1989 was not only hard to move in, but rendered him nearly unable to hear while wearing it.

Photography: Warner Bros. Pictures

Michelle Pfeiffer's Catwoman suit may have looked great, but it wasn't comfortable either. "They had to powder me down, help me inside and then vacuum-pack the suit," she says.

Photography: Warner Bros. Pictures

Most superheroes trace their origins back to comic books, but not Harley Quinn. She was originally created as a one-off character in Batman: The Animated Series but is now firmly etched into the Batman's mythos.

Photography: Warner Bros. Pictures

Danny DeVito says it took four-and-a-half hours each day to get "pounds and pounds of face prosthetics and body padding" to turn him into the Penguin each day.

Photography: Warner Bros. Pictures

Arnold Schwarzenegger needed 7 different Mr. Freeze costumes for Batman & Robin. Each one was made using 500 hand-hammered aluminum parts 10,000 blue LED lights.

Photography: Warner Bros. Pictures

It's hard to look tough in Robin's getup, but make no mistake -- Burt Ward was as tough as they come. He did most of his own stunts and ended up in the emergency room multiple times while filming the iconic live-action series in the 1960s.

Photography: Flickr