The stars shocked fans at New York City gay par Pieces on Friday night, as they hit up the venue for a little late night fun.
An eyewitness tells ET that the friends arrived with a group, and stayed under the radar until they started playing drinking games with the bar's drag queens. "No one really noticed they were there until the drag queen asked to do a game and Adele volunteered," the eyewitness says. "All of a sudden, I see Adele on stage and was like, 'WTF? That’s Adele!'"
The GRAMMY-winning singer took the stage, introducing herself as a "stay at home mom." While she told the crowd she was happily married, she insisted she was "f**king obviously" still there to party it up.
Lawrence, however, wasn't pleased with her pal losing musical shots, playfully tackling her in videos fans posted online.
"Jennifer, this isn't the Hunger Games!" drag queen Brita Filter jokingly yelled. "If Jennifer wants to come and play, she's more than welcome."
That's when Adele jumped in, telling everyone that her friend was "f**king engaged." "You're not even relevant to be here!" she cracked.
But as Lawrence -- who recently got engaged to Cooke Maroney -- told the crowd, her new relationship status had "nothing to do with my drinking abilities!"
A second eyewitness tells ET that Adele and Lawrence were "definitely having a really great time." When it was time to leave, the stars made a quiet exit. "They snuck behind where the queens usually get ready behind the stage and out the front entrance," the eyewitness says. "They were giggling and laughing; it was really cute.”
Lawrence and Adele -- who also hit up Alan Cumming's Club Cumming in NYC -- have known each other for years. They met at the 2013 Oscars, where the 30-year-old singer won Best Original Song for "Skyfall" from the James Bond movie's soundtrack. Lawrence, 28, also took home an award that night, for Best Actress for Silver Linings Playbook.