Late Show with David Letterman: Leon Pendarvis sits in for Paul; it's "Big Comedy Monday," as Gerard Mulligan is the bride to a wedding, Biff gets soup with Lemon Pledge at Rupert's, and Jay Johnson is soaked with iced tea; visiting “Late Night” sidekick Andy Richter returns an ashtray from Dave's term at NBC. claiming he found it in his NBC office, when the new "Late Night" crew was moving in.