4. Conan O'Brien The Office (US)
Episode Appeared: Valentine's Day (Season 2) This is a quick cameo that only lasts for a few seconds. O'Brien doesn't speak any words but the cameo still ends up being awesome. While on a trip to New York City, Michael Scott pays a visit to Rockefeller Center and while outside he thinks he sees Tina Fey. He runs up to the woman and it turns out that it's not her but in the mean time, Conan walks right by, only being noticed by the cameraman and us, the audience. I wonder if this cameo was planned ahead of time or if they showed up to shoot and Conan happened to be there. It would be cool if they showed up and just said "Hey, want to just walk by for a few seconds?"