Jack Black turned a humble office assistant into an unlikely hero on the set of new comedy NACHO LIBRE when he couldn't find a portly stuntman to double for him. The SCHOOL OF ROCK star admits he searched high and low to find a chubby stunt ace - but they were all too "super muscly" to play rotund Black. He recalls, "I'm shirtless for most of the movie so it was hard to find a stuntman who had my same, exact shape. "But we found this guy who was working in the (studio) office; he was like the official Xerox machine copier guy. I was, like, 'Wait a second! Take off your shirt, dude,' and we stood next to each other. "I was like, 'Yep, lucky day for you! Go catch on fire and run across the street.' He had to do a bunch of stuff, but he was into it. Tom Sellitti, thanks dude." Sellitti came in handy again when Black appeared on MTV show TOTAL REQUEST LIVE yesterday (09JUN06) when he stood in for the actor during a surfing wave machine stunt at the show's San Diego, California beach house location.