Anything and everything is up for grabs in the hour-plus riffathon here in Montreal called Stiles & Proops: Unplanned. As the sign behind Ryan Stiles and Greg Proops reads: "Two Guys. One Sofa. No Script." Both skilled improvisers, Stiles and Proops have no problem carrying a conversation and letting it go wherever it may lead, and using any possible distraction to their advantage -- whether it's a couple who arrived late or a woman from the night before attempting to call them out for repeating themselves (they weren't). Each night, they invite an audience member onstage to sit on a stool and write notes and other topics on a whiteboard. Each night, too, includes a mystery celebrity guest. Last night, director Jason Reitman got talked into singing with Stiles and Proops (though they let Reitman off the hook after a couple of lines). Fellow Whose Liner Colin Mochrie also happened to be in the audience last night, and sure enough, he got beckoned down to chat for a bit. Did you know that Canadian TV (CTV) had Mochrie host Are You Smarter Than A Canadian Fifth-Grader? It only lasted five episodes. "They were worried too many people would win," Mochrie said. Since Mochrie was hosting the equivalent of Jeff Foxworthy's show in the States, Stiles tried to goad Mochrie into telling some "You know you're a Newfie" jokes. Newfie, for us Americans who don't follow such matters, is short for Newfoundland. OK. We also learned that Mochrie, who played a Nabisco "snack fairy" in TV ads, took part in a New York City parade for Madison Avenue ad icons, which was weird for him, as people would shout, "Hey, Mr. Clean! Hey, Mr. Peanut! Hey...Colin!" Some joking about the Whose Line "hoe-down" song format -- is hoe-down a song genre? exactly -- and Mochrie joined Stiles and Proops for an ode to Montreal, with Mochrie getting off the best and timeliest quip about being more popular than Paul McCartney in Quebec City. From Reitman, we learned that he is working on an adaptation of the book, "Up in the Air," and also that the Montreal-born director of Juno is not a fan of Air Canada, and can tell you a joke about it.