John Ritter will use his day off from Broadway's The Dinner Party to play guest host on "Live with Regis & Kelly." Ritter will be filling in for television talk show's usual master of ceremonies, Regis Philbin. Co-host Kelly Ripa will be present as usual. "Live with Regis & Kelly" airs on ABC TV 9 - 10 AM. Ritter is expected to stay with The Dinner Party through the current season. —By Robert Simonson