The clip is hilarious in its own right, but it's funnier if you're in on the joke. This is called being RuddRoll'd, a term I learned from the essential Slade Sohmer, which describes the running late-night joke Paul Rudd has with Conan:
Every time Rudd shows up on Conan he comes with "a clip," but that clip isn’t from one of his movies, it’s from Mac and Me, a 1988 science fiction adventure movie where a character races out of control in a wheelchair.
Here's Paul Rudd in action, but I think he's been topped here.