George Clooney has a long and illustrious career as an actor, but it’s arguably dwarfed by his career as a prankster. Over the years, Clooney’s developed quite the reputation for practical jokes by doing everything from tricking Sandra Bullock into jumping into a pool to constantly tormenting the producer of the Ocean’s movies, and he’s definitely not done yet.

During a recent appearance on Jimmy Kimmel Live to promote his movie Tomorrowland, Clooney talked with Kimmel (a fellow prankster who’s famously asked viewers of his show to do things like claim they ate all their kids’ Halloween candy) at length about the various pranks they’ve collaborated on, then revealed that he’s got something very big cooking, something so big that it’s in the homes of the Hollywood elite even now.

“Right now I’m doing something so heinous and so horrible that there are many famous people all across this town right now who have framed photos of this hanging on their wall and don’t have any idea what I’ve done,” Clooney said. “It’s horrifying.”

Clooney didn’t reveal exactly what he’s up to, but here’s hoping someone who’s got one of those photos in their home will eventually figure it out. For more of Clooney’s prank prowess, including the time he failed to prank Tina Fey and Amy Poehler for their Golden Globes jab at him, watch the video.