Stern was a guest on the CBS show Wednesday. The two congratulated each other on their improving looks with age.
Letterman proved it by displaying a picture of them from when Stern first appeared on the then-NBC show in May 1984. Letterman had a bushy head of hair while Stern sported a mustache.
Stern didn't care much for the picture, bus he recalled how grateful he had been for the invite.
"Back then, the fact that you asked me to be on a national television show was mind-blowing to me," he said.
Letterman also brought some of his long-time employees onstage to present the "Top Ten Things Staffers Would Like to Say to Dave on his 30th Anniversary in Late Night."
The Associated Press contributed to this report.