Buffy The Vampire Slayer

In “Xanadu” did Clinton McClung a midnight sing-along decree.

The guy who got people to sing along to the musical episode of “Buffy the Vampire Slayer” (”Once More With Feeling”) has sunk his teeth into a new audience-participation project — and this time, he has to believe it’s magic. Or something. (McClung also has his eyes on Joss Whedon’s new Web series, “Dr. Horrible.”)

“Xanadu” as a movie was a bomb, but “Xanadu” as a camp classic has lived on. Five songs from the 1980 soundtrack were bona fide top 20 hits, and nearly 30 years later, it’s spawned countless YouTube tributes/parodies and become a surprise hit on Broadway. “Do you love it — or do you love it?” Perez Hilton asks on a banner ad outside the theater. Even Joss Whedon threw a “Xanadu” reference into the latest “Buffy” season-eight comic, when one character alerts the others, “Oh, and an angry spirit is attacking the cast of ‘Xanadu.’ Don’t ask me why.” (”It’s a little out-of-date, but what the heck?” Whedon said. “That’s actually a shout-out to my friend James Carpinello, who was supposed to star in the play, but fractured an ankle and a leg while on roller skates right before opening. I had some other friends with roller-skate injuries, so I put that in there.”)

Angry spirits or no, the first sing-along to Olivia Newton-John and the Electric Light Orchestra soundtrack is scheduled for July 18 and 19 at New York’s IFC. “I would assume they’re singing along with a showing of the movie, not a performance of the play,” Whedon joked, “because it would be rude to do in the theater.”

Don’t worry about the “Xanadu” sing-along being yanked for rights issues, the way Buffy was. That had to do with transferring something made for television to a theatrical setting, and as “Xanadu” was created for the movie screen, “there are no rights issues,” McClung said. “We’re doing a movie as a movie, with a fun twist.”

There have been sing-alongs in other cities and in other theaters for “Xanadu,” but McClung hopes to build this one “Rocky Horror”-style, gradually adding a cast and a full onstage production, which could tour the country as the “Buffy” sing-along did. “If this is a big success, à la Buffy, we will amp it up,” he said. “But I may limit it to just a few stunning ensemble musical numbers so as not to overshadow the Broadway show.”

Speaking of which, the Broadway version of “Xanadu” is not only giving a thumbs-up to the sing-along, but is also providing tickets to the show as giveaways. And in the goodie bags, you’ll find kazoos, poppers, bubbles and glow sticks “to give that magical muse effect,” McClung said. “I would love to give everyone a mini-disco ball as well, but I have yet to find a supplier for those.”

Don’t expect karaoke-like subtitles, at least not at the first screenings, because that was the one glitch in getting the rights. “The studio has to do some clearances for that to be allowed,” McClung said. For those less familiar with the soundtrack, there will be lyric sheets as refreshers and, at certain points, cue cards. “Pretty much everyone knows the tunes anyway,” McClung said.

You won’t make a mistake — they’ll be guiding you.