It is one of the most iconic cartoon portrayals by a Hollywood star ever, but now Mark Hamill has revealed some classic movie monsters helped him create his version of the Joker.

Since his inception in 1940, the Joker has become Batman's most formidable foe. The Clown Prince of Crime has been portrayed by the likes of Jack Nicholson, Heath Ledger, and Jared Leto, but in cartoon form, no one can top Hamill's unhinged performance. Just as Kevin Conroy has cemented himself as one of the great Batman vocal artists, Hamill has become synonymous with playing the Joker.

More: Gotham: Mark Hamill Praises Cameron Monaghan’s Joker

Now, speaking to Sway's Universe, the 66-year-old confirms who (or what) was his biggest influence when voicing Mr. J:

“I would imitate the old Universal horror films and I realize, in retrospect, I wasn’t doing it consciously, but Claude Rains as The Invisible Man…[imitates Rains] ‘Crazy? You think I’m crazy? I’ll show you who’s crazy!’ So he had sort of the grit that I incorporated into it and I said to voiceover people later, I would do a character, and I would say, ‘It’s sort of like Howard Cosell meets Jay Leno, is that a cheat?’ And they said, ‘No, we do that all the time.'”

He went on to reveal that it wasn't as simple as just plucking one person from a crowd and saying 'That's my Joker':

"I would say, with the Joker, he's different every time you play him. You try and play him like the first time you've ever done it. In one script, he's meant to be really menacing and another was a parody of Thelma and Louise where Harley and Ivy teamed up and Joker was left shuffling around the apartment in furry slippers and totally cuckolded, so he was played as kind of a goof in that one. So he's different every time. That's the way I look at it. But, boy, I've had so much fun doing it.”

Joker laughing with a hat on in Batman: The Animated Series

Just like Joker is an icon of DC's Batman universe, the Universal monsters became legends of the horror genre. Hamill clearly put a lot of work into playing Joker, rather than just using his everyday voice. Hamill's performance has been credited as one of the best Joker portrayals, and alongside playing Luke Skywalker in Star Wars, fans can't seem to get enough of his skills. Whatever his Joker influence, it worked.

First taking to the role in Batman: The Animated Series, Hamill replaced Tim Curry who was originally cast. However, as soon as Hamill put his distinct vocals to the part, everyone forgot that Curry was ever a contender for the role. As The Animated Series continued and bowed out, something clicked between Hamill and the Joker, being a part he still voices to this day. As well as returning to the role for the likes of Batman Beyond: Return of the Joker and Rocksteady's Arkham games, Hamill recently played Joker again for the R-rated Batman: The Killing Joke and the ongoing Justice League Action.

When Bill Finger created the Joker, he reportedly tried to channel 1928's The Man Who Laughs - featuring a disfigured man with a bleached face and fixed grin. Across all those who have played Joker the years, each has had a difference muse. Ledger reportedly took a little of Alex DeLarge from The Clockwork Orange and Leto channeled David Bowie. However, Jay Leno? That's got to be a new one!

More: Sean Penn Says Chris Nolan Never Offered Him the Joker Role

Source: Sway's Universe