Louis C.K. made an unannounced appearance at the Comedy Cellar on Sunday night, according to the club’s owner, performing for apparently the first time since he admitted last year to sexual misconduct with women in the comedy world.

He appeared around 11 p.m., said Noam Dworman, the owner of the Cellar, the Greenwich Village club with a long tradition of surprise appearances by famous comedians. Dressed in a black V-neck T-shirt and gray pants, he did a 15-minute set that touched on what Mr. Dworman called “typical Louis C.K. stuff” — racism, waitresses’ tips, parades. “It sounded just like he was trying to work out some new material, almost like any time of the last 10 years he would come in at the beginning of a new act.”

Mo Amer, another comic who was on the bill Sunday, said that for the crowd, “it was like a wow moment.” He, too, said he had no idea that Louis C.K. would return that night but that his material was “like, classic Louis, really really good.”

[Read more: Louis C.K. is accused of sexual misconduct.]

Mr. Dworman said Louis C.K. “was very relaxed,” and the audience, a sold-out crowd of about 115, greeted him warmly, with an ovation even before he began. (Mr. Dworman was at home asleep, but club staff texted him about the appearance, and he later watched a tape of it, he said.)