The Joker’s laugh
Look, if you grew up watching Batman: The Animated Series, you know that Mark Hamill voiced The Joker. It’s one of the best versions of the character ever put on screen, and Hamill’s voice is the gold standard of voicing The Joker to this day.
What you might not know is how Hamill developed The Joker’s signature laugh. According to Hamill, he would practice it while driving in a convertible in Los Angeles. And in classic Los Angeles fashion, apparently no one seemed to care/was bothered by Hamill doing this.