UFC fighter Fabricio Werdum, a big fan of the Halo series, will play a voice-only role in Halo 5: Guardians, Microsoft has confirmed.

Werdum’s part in Halo 5 was not immediately made clear, but Microsoft did say you’ll have to do some hunting to discover where the 38-year-old heavyweight champion shows up.

“Fabricio Werdum makes a small, voice-only cameo appearance in Halo 5: Guardians,” a Microsoft spokesperson said. “He’s a big fan of Halo and we’re big fans of his, so it’s always fun when these kinds of things work out. It’s a bit of an Easter egg though, so you’ll have to really be looking for it.”

Werdum’s involvement in Halo 5 was first reported by The International Business Times.

The Halo franchise is no stranger to celebrity cameos, as Conan O’Brien and Andy Richter appeared in Halo 4 as two marines who crack jokes about rugs and awakening aliens from an ancient slumber.

Outside of Halo, this year’s Call of Duty: Black Ops III will feature a character played by star NFL running back Marshawn Lynch. Meanwhile, celebrities like Jeff Goldblum, Ron Perlman, Neal McDonough, and Heather Graham will appear in the game’s new zombies mode.

Halo 5 launches on October 27 for Xbox One.