The comedian – who just received her first-ever best actress Golden Globe nomination – was joined by a group of friends at the bar after her stand-up performance.
“All she wanted to do was have a glass of wine with her entourage,” a customer at the lounge tells PEOPLE.
The 34-year-old then, unexpectedly, began to sing a version of Jefferson Airplane’s 1967 hit “White Rabbit,” according to the patron.
They add, “She sounded great.”
The source adds that, “Amy is really pretty in person and had beautiful skin.”
After more bar-goers recognized the star, however, she decided to leave with her staff.
“Amy had fun while she was here,” the source says.
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Schumer shared a photo of herself from her Fort Lauderdale visit to Instagram on Sunday, as well.
In the photo, the Trainwreck star banged away on a drum set. It’s unclear where in the city the photo was taken.
“Thanks ft lauderdale.,” she wrote. “Much love!”
The actress will go head-to-head with her BFF Jennifer Lawrence at the January Golden Globes, as the women are nominated in the same category.
Lawrence joked to E! News this weekend that she and the actress will wear the “exact same thing” for the ceremony.
“I’m just going to have to have Dior make two of whatever they’re making for me,” Lawrence said, as she is one of the celebrity faces of the designer.