Rise to Fame
He co-created It's Always Sunny in Philadelphia from a home video Rob Mac shot with Day and Glenn Howerton on a consumer camera with essentially no budget. FX picked it up in 2005. Day plays Charlie Kelly, co-writes, and executive produces, and the show became the longest-running American live-action sitcom in terms of seasons when it hit season 15 in 2021. He's said he almost left multiple times to chase a film career, and Horrible Bosses and Pacific Rim kept him credible. But Always Sunny was where the actual work was.
In the Spotlight
He's been testing whether he can operate outside the Always Sunny sandbox, with reasonable results. Honey Don't! (2025), an Ethan Coen neo-noir with Aubrey Plaza and Margaret Qualley, premiered at Cannes to a standing ovation. He's reprising Luigi in the Super Mario Galaxy Movie for 2026. He co-created Mythic Quest for Apple TV+ (2020-2025) while publicly saying the comedy film lane he'd once wanted has basically closed. Staying put turned out to be the smarter move.
Side Notes
His real-life wife, Mary Elizabeth Ellis, has played The Waitress on the show since 2005, the woman his character has spent twenty years pathetically failing to woo. They met in 2001, before the show existed, and married in 2006. His parents are both music teachers, his father a professor at Salve Regina University, and he studied art history at Merrimack College. He got his first agent performing a blues song he'd written at a cabaret night, which is somehow the least surprising detail once you've seen the show.