"I don't know if I can look you in the eye anymore," Roberts quipped on the air. "Last time I saw you, you were single and then I, like, hypnotized you in my white suit or something and you went off and married Regina (Lasko.)"
She then asked the talk-show host several questions about his March wedding, including, "Did she take your name?"
Letterman said she did, prompting Roberts to inquire, "So, she's Mrs. Letterman?" to which he replied, "No, she's Dave."
The host said the fun part about his wedding was having his son Harry attend.
Roberts then asked, "What did he think you were doing?"
Letterman joked, "Well, he thought I was getting my driver's license renewed."
He then explained the service "was me, it was my son, it was Regina and the justice of the peace, and that was it. ...
"I mean, it's legal, that's the most important thing, right?"
"You're bound for eternity," Roberts agreed and Letterman said, "That's right, and never been more deeply in love."
The audience applauded and the actress laughed and called Regina a "lovely and, no doubt, tolerant woman."
"Yes, and I know she's watching at home," Letterman said.
Rosie O'Donnell unveils nearly 50-pound weight loss
Justin Bieber crashes Drake Bell's album release party