David Letterman told Justin Bieber he could smell a weasel when the pop star was accused of fathering a fan's baby.

In a preview of The Biebs' appearance on The Late Show with David Letterman Wednesday night, Letterman describes his anger at Mariah Yeater's paternity claim.

Letterman may be unusually sensitive to the possibility of people trying to extort money from celebrities: In 2009, he admitted to having sex with women who work for him on the Late Show after one of their boyfriends tried to blackmail him.

You know what? That made me see red, Letterman told Bieber about Yeater's claim of a backstage tryst with Bieber after a Los Angeles concert.

Really? You saw red? You were angry? Why were you angry? a smiling Bieber asked Letterman.

I could smell a weasel, said Letterman.

I think I can smell a weasel, too, a little bit, Bieber said. I know, it's pretty crazy ... people make up false accusations.

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