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Tina Fey strips down to her Spanx in honor of David Letterman

Tina Fey is such a fan of David Letterman that she gave him the dress off her back!

Looking stunning in a skintight blue and black getup, Fey pointed out to Letterman on Thursday's "Late Show" that she doesn't dress this nice for just any host. Letterman was impressed, comparing the "30 Rock" star to the Duchess of Cambridge, Kate Middleton.

"I dress up like this out of respect for you," Fey said. "What, am I going to put on a dress for Jimmy [Fallon]? That's creepy. He's like my brother. What, I'm going to wear special underwear for James Corden?"

That being said, the dress had to go. "Because this is my last time wearing a fancy dress on a talk show and conforming to gender norms out of respect for you," Fey explained, "my gift to you is I want to give you the dress."

Letterman then helped Fey unzip her outfit, revealing the Spanx underneath. The front of her garment read "Bye Dave," and when she flashed her bum it said "#LastDressEver."

It's going to be hard to top this farewell!

Letterman's last "Late Show" airs May 20 and is expected to be a bittersweet show.