In over-the-top scenes, Norbert Leo Butz and John Lithgow — who are both nominated for 2005 Tonys in the category of Best Leading Actor in a Musical — play con men who variously masquerade as a disabled veteran, a sadistic German shrink, an exiled prince, a mentally-shrunken little brother and more.

This isn't exactly Hamlet. Think more like "The Carol Burnett Show."

Do the daffy situations and the waves of laughter ever prompt the actors to perhaps expand their performances on certain nights?

"It's a nightly challenge between letting it be spontaneous and fresh and new, and yet to stay within the reigns of believability," Butz told Playbill.com. "It's a dangerous thing; a laugh can be very, very narcotic — addictive."

In a comedy so broad, is there an urge to go bigger? "It's crazy material, but it's rooted in everybody's wants and needs," said Lithgow. "Anytime you rehearse comedy it's always a good idea to go as far as you can. I'm a great believer in wild excess, as long as you're rehearsing. But then you absolutely depend on your director to edit that."

In the fall 2004 tryout of Dirty Rotten Scoundrels at San Diego's Old Globe Theatre, Tony-nominated director Jack O'Brien would often invite the actors to "pull back" and let the writing be funny rather than the performances, the actors said.

"If you look at Dirty Rotten Scoundrels, there are lots of moments of quiet," Lithgow explained. "You need to give the audience a chance to breathe. You also have to remind them what the emotional stakes are. There was a great rehearsal day after we started previewing in San Diego, where Jack said, 'OK, from this day on, we go deep.' We worked closely with the [Tony-nominated] book writer Jeffrey Lane and suddenly all this material appeared about the characters: Freddy's grandfather, my character's feelings of autumnal melancholy, all those things that counteract and give a real emotional foundation to the wild comedy."

Were there explorations of characters' "back story" — the characters' histories?

"It wasn't back story as much as looking at what the stakes are," Lithgow said. "The play is a sort of meditation on the confidence game: As soon as you fall in love with somebody, you're an easy mark. You've got to really believe in that falling in love…the audience has got to believe it."

Lithgow said he wasn't aggressive about the exploration of back story.

"We certainly talked about it, but it's not exactly Strasbergian sense memory," he said. "This is a vaudeville, for heaven's sake! I'm beating someone with a stick in one scene, after all."

Given the wildness of the comedy, do Butz and Lithgow crack each other up? Have there been crazy, comic, train-wreck moments?

"It is always crazy," Lithgow said. "There are moments. It's such a high-wire act that if the tiniest thing goes wrong, you fall into the net. There was one day when I came out for one of my last scenes. My line was, 'My God, where's Freddy?!' And from the preceding scene, where Freddy takes all his clothes off, his shoe was still lying on the stage. Somehow, it had slipped off the revolve. There was his shoe. I knew I had to be the one to throw that shoe into the wings. Well, that cost us about five minutes of laughing on stage. When that happens, you just pray that Jack O'Brien isn't in the audience."