All four Seinfeld principals  Jerry Seinfeld, Julia Louis-Dreyfus, Jason Alexander and Michael Richards  will reunite on Live with Regis and Kelly on Nov. 23, in an outing devoted entirely to the hit sitcom (and, namely, the DVD release of Seasons 5 and 6).... Look for South Park's Chef, Isaac Hayes, to serve up a hilarious musical number on a spring 2006 episode of That '70s Show.... Grey's Anatomy star (and aspiring road racer) Patrick Dempsey will appear on Speed Channel's Test Drive on Nov. 20.