Guillaume Cassuto is a London-based graphic designer, writer, and compositing supervisor for The Amazing World of Gumball. He started off making backgrounds for the show since Season 2, but was switched to writing episodes of the series. He also had an idea for an episode called "The Hug."
He has since left production for The Amazing World of Gumball on October 26, 2017, describing the show as his "most ambitious and fulfilling project" he has contributed to. He is currently working on his new Cartoon Network show Elliot from Earth along with the rest of the Gumball team.