Hamill got his role in Star Wars mainly because he could say the rather pretentious lines like he believed them. He describes himself as just a fanboy who got lucky.
His voice work goes back to 1973 when he did a few episodes of Scooby-Doo but it really took off after he played the Trickster on the short-lived live-action Flash. Until then people still typecast him as a hero but his version of the Trickster was so over-the-top that he was cast as the Joker for the animated Batman. He continues to be the voice of the animated Joker along with a long list of other voicework.
In 2004, Hamill and some fellow voice artists improvised a movie at the San Diego Comic Convention. It was entitled Comic Book the Movie and I swiped it for the name of this blog.