Michelle Obama on Letterman: 'This Isn't Oprah!'

In her debut appearance on CBS' "Late Show," Michelle Obama had one question for host David Letterman: Where are the laughs?

In an early released clip of the interview, which airs tonight, the first lady talked about her father's battle with multiple sclerosis.

"I never knew him to be able to walk, but my dad worked so hard and he loved us so much, and I think from him I learned just absolute, complete unconditional love, the notion that kids really don't need anything but to know that their parents adore them," Obama said.

"I think that's the greatest gift they gave us, just their constant support and, you know, stability, and that's really what we try to instill in our girls," she added. "I mean, you talk about raising kids, it's just really - you know, we had rules, we had boundaries, but there wasn't anything my dad wouldn't do for us, and, uh - don't make me cry."

Recognizing the conversation had taken a turn for the serious, Obama exclaimed: "This isn't 'Oprah!"

"It's supposed to be 'Letterman.' What's up? Where are the laughs?" she said.

"Did somebody tell you this was 'Oprah? Is that why you're here?" Letterman said. "Oh my, someone misled the first lady."

There were, of course, plenty of laughs as the first lady showcased her comedic, and sarcastic, side.

Pressing Obama about her private conversations with the president, Letterman asked, "Hypothetically speaking, at the end of the day… has your husband ever come home and said to you, 'Oh, that John Boehner, what an idiot.'"

The first lady laughed.

"It has never happened, never, never," she said, shaking her head. "He is always upbeat, particularly about Congress."

"Yeah, how can you not be upbeat?" Letterman said.