As Conan O’Brien promos his well-reviewed Can't Stop doc (and bathes in the glow of his widely viewed Dartmouth commencement address), the funny cable talk show host is set to add acting to his resume. Well, not exactly. He's going to play a lowly extra on comedy TV series How I Met Your Mother. Why? He won the walk-on role at a charity event. Rather than perform a showy celebrity cameo, O’Brien, who is 6' 4" says: “I think it's much funnier if I'm just in the bar, in the background."