HER studio apartment in Williamsburg, Brooklyn, is just shy of 400 square feet, barely enough room for an Ikea open-shelf bookcase, a chocolate-brown tufted couch, a full-size bed and her brindle-coated Shih Tzu, Charlie.

So when Claudia Argiro, 33, gave a holiday party last Saturday night, she pared down her guest list to about two dozen of her closest friends, hid the TV behind an industrial column wrapped with holiday lights and turned the media console into a bar.

But one thing she had to have was a bartender. “I’m an adult now, living by myself, and this is my sh-bam, my moment,” said Ms. Argiro, who runs a clothing boutique nearby called Charlie and Sam.

She called up Tealicious, a catering company in Queens, which sent over Eric Villani, a 33-year-old bartender, who was stationed in a two-foot-wide triangle in the middle of the room. For the next four hours, Mr. Villani stood there, not to make special cocktails, but to pour a vodka punch or a rum eggnog into clear plastic cups, trimmed with sugar-coated cherries and cinnamon sticks.