NYC's Comedy Cellar is no stranger to surprise sets from huge comedians, but it's a rarer case when a whole posse show up at the same time. Tuesday (9/26) was one of those nights. Madonna, Amy Schumer, Aziz Ansari, Jon Stewart, Pete Holmes and Louis CK all showed up. Madonna, who had Amy Schumer open for her at MSG, and who did a surprise opening set when Amy later headlined MSG, made her comedy debut at the show. She wrote on Instagram, "And the next minute I was tagging along with Amu Schumer at Comedy Cellar making my stand up debut! What a thrill. Finally busted my cherry. Thank you Amy!" Amy also posted an Instagram of her own, adding, "We'd like to thank Comedy Cellar for taking a chance on our new act."

Here are some more photos and videos of the star-studded night: