Buffy The Vampire Slayer

At a sing-along inspired by “Buffy the Vampire Slayer,” fangs, bubbles and a sold-out crowd.

THE lights had just dimmed when a young woman wearing a flowered dress made her way along the first row of seats of a theater at the IFC Film Center in the West Village with a pile of dry cleaning in her arms. “Do you want to dance on stage with us during the ‘They Got the Mustard Out’ song?” the woman whispered to members of the audience as she handed out freshly laundered shirts.

“They Got the Mustard Out,” a little number about the joy of having a competent dry cleaner, is not part of a new musical about the daily grind of living in New York. On the contrary, it is part of a sing-along inspired by “Buffy the Vampire Slayer,” the cult television show about a tough young blonde who, along with her nerdy friends, fights demons and vampires in Sunnydale, Calif., her fictional hometown.

With a tip of the hat to “The Rocky Horror Picture Show,” which set the bar for audience-participatory midnight screenings, the sing-along is based on “Once More With Feeling,” a musical episode from the show’s sixth season. The event is the brainchild of Clinton McClung, a 36-year-old film programmer who lives in Prospect Heights, Brooklyn, and whose preference for sweater vests and tweed jackets makes him a natural for the role of Buffy’s bookish “watcher,” Rupert Giles.

Mr. McClung created the sing-along in 2004 when he worked at the Coolidge Corner Theater near Boston and brought the show to New York when he moved here last summer. Ever since, this “Rocky Horror Picture Show” for the postmodern set has been gaining steam, with the February rendition marking the fifth monthly, over-the-top, costumed, live-cast, sold-out, audience-interactive midnight performance.

“It’s all for the love of Buffy right now,” Mr. McClung says. But the sing-along has fast become his (mostly unpaid) full-time job, and as word spreads, he is ushering it onto stages around the country. The show has played in Huntington on Long Island, Chicago, Tucson, Pittsburgh and Austin. Mr. McClung, who said he has a licensing agreement with the distributor of the television program, is planning a national tour this summer.

What audiences around the country will see is the sort of thing that took place at midnight last weekend, when 200 people braved 10-degree weather in a line that snaked two blocks down the Avenue of the Americas, waiting for the theater to open.

Nerina Garcia, a psychology graduate student at Fordham University who described herself as “in love with ‘Buffy,’ ” was huddled in line with her boyfriend. “If you really analyze each episode, it’s not just superficial,” she said. “Every time I watch it, there’s something deeper.”

Each guest received a red plastic goody bag filled with bubble soap, vampire teeth, party poppers shaped like champagne bottles, and a rule sheet. The first rule: sing along. Others included shouting “Shut up, Dawn!” in response to the comments of Buffy’s clueless younger sister, played by a 23-year-old business analyst named Meghan Wherrity. The bubbles were for use during a ballet number - “to give it a Lawrence Welk feel,” Mr. McClung explained. The champagne poppers were to be popped at the “ahem, climax” of a love song.

After a round of “Buffy Jeopardy,” the room went dark. In this episode, a musical demon causes the residents of Sunnydale to sing and dance their secrets, sadness and joys. As the intricately choreographed numbers played on the big screen, a ragtag and goofy approximation of the show proceeded on stage below. The audience responded by singing, shouting lines along with and at the characters, waving lighters, and making a wave with their goody bags during a number called “Walk Through the Fire.”

At evening’s end, fans trickled reluctantly back into the cold. Among them was Joy Abella, a 33-year-old advertising account supervisor. The next day, Ms. Abella said, “I called my sister up, and I said, ‘Sheer genius.’ ”