Amy Sedaris pulled on a pair of Weekender pants and all bets were off on 'Late Night' (Weeknights, 12:30AM ET on NBC). What happened next genuinely defies description, as she displayed moves and flexibility that had Jimmy Fallon falling off his chair with laughter.

Even comedian Will Forte, on the couch, had no idea how to react or what to do. Everything felt so completely inappropriate, and yet it really wasn't. What Sedaris was doing, though, was showing us the stretch, comfort and versatility of the pants.

"These work because they have an inside pant," she said striking a pose. "You know what I mean? So you wear them all weekend."

Fallon didn't really know what she meant, so she further explained. "You don't have to change your underpants. It's all built in!" Doesn't that sound ... well, a little bit gross, but Amy still makes them look so fun!