Mary-Kate Olsen is en fuego these days. First she proved that she's able to smile without looking like Renee Zellweger, then her Wackness co-star Ben Kingsley announced she is quite the siren when it comes to on-screen kissing skills, and now she's teamed up with David Letterman to slowly and swiftly decapitate Hills villain Spencer Pratt. On Dave's couch to plug her film, MKO's stoner voice waxed rhapsodically about her hippiefest of a birthday celebration at Bonaroo, and what it was like to, as Dave put it, "kiss a really old guy." But things turned far more interesting after Olsen slyly inserted the robotic nobody Pratt into the conversation. And Dave couldn't have been more pleased. Hear what MK had to reveal about going to high school with Pratt, and join us in applauding her ability to spark an insult-laden bout of commentary from Dave regarding the "wormy," "oily" Pratt.

Though we're sure Mary-Kate and Dave, evoking more chemistry as a comedy duo than Dave and Paul ever have, planned the awkward set-up in advance, Letterman's inquiry into Mary-Kate's famous high-school buddies not-so-surprisingly led to Olsen spilling the beans on Pratt's notorious "temper" while playing for her school's soccer team. According to MK, Pratt would get in violent fights with the coach and walk off the field in huffs regularly. Dave excitedly jumps in with a series of convoluted and delightful questions like, "How does someone his age get to be so oily?" and "Isn't he wormy?" Olsen, just on the verge of participating in the rant, impressively takes the high road by successfully pulling off a (funny!) non sequitur into promoting her film. Her old lady posture aside, Olsen has officially unveilied her A-game these last few weeks. If only she would come back to Weeds and save the Botwins from Mexico captivity by distracting the border guards with her hypnotizing laughing shoulder heaves, we might even throw a few buckets of red paint at PETA members in her honor.