The cast looks like they may have come from the best little whorehouse in Texas, but she warns the audience against making any unsolicited moves.

“This is like a high-class strip joint,” she says. “We can touch you, but you can’t touch us.”

She then pulls open her shirt, winding up with a fellow crew member’s head in her cleavage.

Rocky fans wave dollar bills in the air to buy a “bag of shit,” containing everything they will need for the next two hours—a ziplock bag of rice, toilet paper, a noisemaker and playing cards.

But it’s April Fool’s Day, she says, holding up one of the bags: “It could be crystal meth.”

It’s already ten past twelve, and the show is just getting underway. A series of pre-show skits begin as female cast members in black bras and fishnet unitards slink through aisle and gyrate to the beats of “Shake My Booty.” Feathers from purple boas fly in a mock battle between characters from Rocky Horror and Priscilla, Queen of the Desert, an Australian movie about drag queens.

Then it’s the virgins’ turn. Dozens of audience members with red lipstick V’s smeared on their foreheads vie to be pulled on stage in a competition to see who can give the best 20-second lap dance. When audience applause deems Vicki the winning virgin, her row of friends stands and cheers.

The theater dims, and as those in the know wait for red lips to kiss the screen, they yell in unison: “Once upon a time, a long time ago…”

Rocky’s Road

Rocky Horror began on stage as a spoof musical. The film adaptation, starring Susan Sarandon, Tim Curry and Barry Bostwick, flopped in 1975. But the next year, when the Waverly Theater in New York showed the film as an April Fool’s gimmick, it began its midnight reign.

The horrors begin shortly after Janet and Brad marry and drive off from their home in Denton, Ohio. When their tire blows out, they trudge through the rain to the nearest shelter—a castle owned by Dr. Frank-N-Furter, a transvestite hosting a convention of aliens from the planet Transsexual in the galaxy Transylvania. Tormented and propositioned, the newlyweds are chased by Frank-N-Furter’s creation named Rocky Horror.

And on this April Fool’s weekend, the outrageous plot and its outrageous ’70s music are still going strong in hundreds of theaters across the country.

What keeps it alive is what insiders call “AP,” or audience participation—which means shouting “asshole” every time Brad appears and “slut” whenever Janet shows up, throwing rice around the theater when they get married and tossing chunks of dinner rolls during a banquet scene. Regulars pick up the lines, which vary depending on the theater and some even invent their own.

In the early years, the Exeter Street Theater gave Rocky Horror its Boston home. But when the house folded in 1984, the singing menagerie came to Cambridge.

In Harvard Square, Rocky Horror is serious business.