After the 68-year-old host complemented Fey on her dress, she vowed she would never wear a "fancy dress" on a talk show again — and she meant it!
The Unbreakable Kimmy Schmidt creator explained that she couldn't imagine herself glamming out for anyone else:
"What am I going to do put a dress on for Jimmy [Fallon]? That's creepy. He's like my brother. I'm gonna wear like special underwear for James Corden? That's not gonna happen. The next time you'll see me I'll be playing charades in a slanket."
Since the 44-year-old actress didn't need the dress anymore, she decided to give it to Letterman as a memento — and stripped in front of the entire audience!
Check out the video (below) to see what the funny lady was wearing underneath her #LastDressEver!
And just in case you were wondering, here's what Tina Fey will probably look like from now on only wearing a slanket: