The 2009 Emmys were hosted by Neil Patrick Harris. His internet serial Dr Horrible’s Sing-Along Blog (see my post here) was nominated for an Emmy that year, so it was only natural for him to appear at some point as that character.
Here is the video of Dr. Horrible “hijacking” the Emmys broadcast. (Hey, who knew accountants could be funny?) You can tell from the audience’s reaction that most have no idea who he and Nathan Fillion are supposed to be. They have their personal assistants deal with that “internet thingy.”