During last Friday's taping of the triathlon stunt with Teri Hatcher for his Friday night show, Conan OBrien and Hatcher were running in swimwear through the audience back onto the stage when OBrien then slipped and fell back on his head which caused a concussion.  OBrien returned on Monday night, and of course like every comedian he returned with nothing but jokes and the actual footage of himself when he slipped.  To watch the video, follow the link featured below.