That '70s Show regular Tommy Chong says former comedy partner Cheech Marin is making a big mistake by abandoning the brand of stoner comedy that helped make them stars.

"Audiences come to accept you in a particular way," says Chong, 62, who plays Leo the stoner on the popular Fox sitcom. It's a familiar role for Chong, who helped invent pothead humor back in the 1970s as one half of the comedy duo Cheech & Chong. "They know I represent marijuana. If you start deviating from how they know you, it can kill you.

"Look at Cheech," he tells High Times. "He plays sidekick to Don Johnson. That's not how audiences know him. Once you make your decision to leave the old Cheech behind, it's real hard to come back."

While Marin in recent years has found success in mainstream projects (Nash Bridges, Tin Cup), Chong has been making a living merchandising bong pipes and touring comedy clubs (he'll be at the Funny Bone in South Bend, IN, this weekend). Chong's expressed interest in reviving Cheech & Chong, but Marin will have no part of it.

"He's happy," says Chong. "But I think he made a mistake. We had control over everything we did. I still do. I don't know if he does."