Castle played Michael Myers in the 1978 horror film Halloween, directed by former USC classmate John Carpenter, being paid $25 a day. Castle's subsequent collaborations with Carpenter included his name being used as one of the main characters' names in The Fog, co-writing the script of Escape From New York, and performing the title song of Big Trouble in Little China as part of the band The Coup De Villes, alongside Carpenter and another friend, Tommy Lee Wallace.
Castle's most recent project as a Writer is August Rush, a musical-drama directed by Kirsten Sheridan and starring Freddie Highmore, Jonathan Rhys-Meyers, Robin Williams, and Keri Russell, which was released in 2007. He also stars as himself in the 2010 documentary Halloween: The Inside Story by Filipino filmmaker Nick Noble. On December 20, 2017, it was announced that Castle would be reprising his role as Michael Myers in the new Halloween film .
