Howard Stern -- Appears on tonight's 'Letterman'

Howard Stern was up to his old tricks last night on CBS' "Late Show with David Letterman" – hurling insults at Rush Limbaugh and dishing on his derriere.

Letterman asked the 55-year-old shock jock – who flew into the MTV Movie Awards 17 years ago wearing the "Fartman" costume that exposed his backside – whether he was flattered by Sacha Baron Cohen's copycat prank with Eminem at this year's ceremony.

"I am a bitter man. I am never flattered. I always sit there and go 'I did that! I hope somebody recognizes me for that,'" he said.

And added his stunt was "an innovation that should be honored…revered!" and that unlike 'Bruno's' staged hoax – his had been hidden from producers.

On having more kids, Stern, who already has three grown children, told Letterman, who has a five-year-old son, that the idea of starting all over again was crazy.

"I've seen pictures of you in tabloids…you don't look like you're having fun, my friend." he said.

Stern also talked about his marriage to actress Beth Ostrosky, 36, revealing the secret to the couple's relationship success: trips to the psychiatrist three times per week.

And finally, Stern mouthed off on the state of the radio business. His assessment? It's "in the hole" thanks to conservative radio host Limbaugh, whom Stern described as a "big bloated turd" for his desire to see the Obama presidency fail.