He also lent his voice to Master Eraqus in the English version of the video games Kingdom Hearts: Birth by Sleep and Kingdom Hearts III. Additionally, he provided some additional voices in My Friends Tigger and Pooh, and voiced Colonel Muska in Castle in the Sky, Mayor of Pejite in Nausicaä of the Valley of the Wind, Flint in Buzz Lightyear of Star Command, Zeus and Hans Christian Andersen in The Little Mermaid TV series, Bats Biker and the Shape Shifter in Gravity Falls, ShiverJack in Jake and the Never Land Pirates, Gadfly Garnett in Miles from Tomorrowland, Nightmare in Ultimate Spider-Man, and Ulysses Klaw in The Avengers: Earth's Mightiest Heroes.
He attended the opening of Star Wars: Galaxy's Edge.
Outside of Disney, he frequently voiced the Joker in varying incarnations of the Batman franchise from 1992 onward. He also voiced Niju, the main antagonist of Balto II: Wolf Quest, Ozai in the Nickelodeon series Avatar: The Last Airbender, Undergrowth in the Danny Phantom episode Urban Jungle, Malefor in the video game The Legend of Spyro: Dawn of The Dragon, Skips in the Cartoon Network series Regular Show, and Chucky in the 2019 film, Child's Play.
- Tetsuya Nomura, the director of Birth by Sleep, stated in an interview that he chose Hamill for the part specifically because of his role as Luke Skywalker in the original Star Wars films. Eraqus is rivals with Xehanort, who is voiced by Star Trek actor Leonard Nimoy, essentially making their rivalry Star Wars VS Star Trek to Nomura.
- Hamill stated at Comic-Con 2010 that playing as Luke Skywalker was his overall favorite role.
- Hamill originally wanted to play The Vulture in Spider-Man: Homecoming, only in the case if Michael Keaton didn't accept the offer. Keaton initially turned down the offer to play The Vulture, but at the end, he entered in re-negotiations and ended up portraying the character in the film. However, Hamill had stated that he could play another role in a further Marvel Cinematic Universe in the near future.
- Of his characters, Hamill plays the Joker with a high, squeaky tone, and Luke with a lower, more mature tone.