Justin Bieber has a better story than the one Mariah Yeater has been telling about him fathering her child. On 'Late Show' (Weeknights, 11:35PM ET On CBS), he said he'd preferred the story be "Justin Bieber ran away with a 20-year old supermodel."

What will Selena Gomez say? She's still only 19!

Bieber also had to school David Letterman on how far medical technology has come. Letterman thought Bieber might have been unconscious when he gave a DNA sample, but it was a simple swab in the cheek.

"Is there disrobing?" Letterman asked. When he found out there wasn't, he declared he wasn't doing it, then.