Willis got hired at Ghost Planet Industries after giving the producers a very formal letter of recommendation written in crayon, seemingly by a young child. They liked his sense of humor and hired Willis as a writer for Cartoon Planet in 1995 and then as a writer for Space Ghost Coast to Coast (SGC2C for short) soon after. In early 2000, he helped write and produce the two Brak Presents the Brak Show Starring Brak specials.
Willis was working on Space Ghost Coast to Coast where he first met Matt Maiellaro, with whom Willis would later create many independent short films and eventually create the popular Adult Swim cartoon Aqua Teen Hunger Force. Aqua Teen Hunger Force first premiered unannounced in the early hours of December 30, 2000 and later officially debuted on Adult Swim in the Fall of 2001. In 2005, he co-created the show Squidbillies. His works mostly fall into the genre of surreal humour.
Willis was born in Wichita Falls, Texas, and was raised mostly in Conyers, Georgia. He graduated from Wake Forest University and was station manager at Wake Radio. He resides in Atlanta with his wife and two children, Max and Sadie.