CNN anchor Anderson Cooper grew up wondering whether Cher was his sister.

Cher, who is scheduled to perform at Sunday's Dance on the Pier, which closes New York City's Gay Pride Week, appeared on cabler Bravo's Watch What Happens Live.

Cooper rang the set's doorbell and surprised Cher as she talked with host Andy Cohen.

“Of course, I grew up adoring you and watching you, and my mom [Gloria Vanderbilt] always wanted to have a girl, she had four boys, and so she always called you her 'fantasy daughter,'” Cooper said.

“So, I literally, when I was really young, I grew up thinking like, 'Am I related to Cher? Is Cher my sister? I really don't quite understand this.'”

“That explains …,” Cohen started.

“I don't know what that explains,” Cooper interrupted.

Cher commented on Wednesday's Supreme Court rulings knocking down DOMA and paving the way for the marriages of gay and lesbian couples to resume in California: “It's about time, come on.”

“Actually, they should have never had to do it. We should never have to do that kind of stupid stuff,” Cher said. (The video is embedded on this page. Visit our video library for more videos.)