BUFFY’S PRACTICAL JOKE BACKFIRES

A practical joke backfired on “Buffy the Vampire Slayer” star Sarah Michelle Gellar and co-star Alyson Hannigan, who sneaked up on series regular Nicholas Brendon while he was dangling from a high bar in a gym scene, yanked down his shorts and . . . YEEEooOW! Nick had come to the set “commando” and the girls — suddenly faced with his bare backside — covered their peepers and ran off giggling!