“Once upon a time, a long time ago, in a galaxy far, far away, God said, ‘Let there be lips.’”

And there were lips. Big, blood red lips and sparkling white teeth. Lips that begin mouthing the words to “Science Fiction/Double Feature,” the schmaltzy song that plays a little after midnight every Saturday at the Loews Harvard Square. The Rocky Horror Picture Show swaggers onto the screen, as it has every weekend for nearly two decades.

More than one hundred fans crowd the cinema’s theater number four—from Rocky regulars who have the lines down pat and intone the “once upon a time” in unison, to first-timers there as Rocky “virgins.” Last Saturday, a Boston man decked out in a red sleeveless dress and fishnets sat across from a father escorting a dozen Spanish exchange students from his daughter’s high school and a New Jersey girl passing through town to visit colleges.

Two hours later, they will rush out of the back door onto a desolate Church Street, picking rice out of their hair and brushing after-dinner mints off their laps. The lucky ones might have given a lap dance on stage, bumped pelvises with perfect strangers as they danced the “Time Warp” in the aisles, or received an impromptu serenade from a man in lipstick and a miniskirt. They will have seen one of the greatest cult classics of all time, yelled at the screen and watched a seven-person cast act in sync with the movie’s leading players, strutting through the theater in black bras, garter belts, silk shirts tied high and skin-tight shiny pants.

And, week after week, they will return to Rocky. Long after the horror has worn off, the picture is still playing and the show must go on.

Who Brought Them Here?

It’s 11:30 p.m. and around 50 people are already milling in the street outside the cinema.

Jacob Gastlyn came to Harvard Square in a taxi. He was afraid to take the T from the Fenway stop, he says, because he thought a man in a red sleeveless dress, light blue eyeshadow and black nail polish would get beaten up.

He only dresses in drag when he goes to Rocky Horror, which he has been doing since he attended his first show in 1994, at age 18. At that point, he came dressed in a trench coat as “The Crow,” a comic book superhero. A few months later, he decided to make his drag debut.

“I saw the attention I got, and started to do it a lot more often,” he says, while fidgeting with the padding in his ample breasts. “I’ve been doing it so long it’s comfortable.”

He came to the show Saturday with a female friend, in pigtails and a red dress.

She remembers a month ago when a few parents brought their 12-year-olds to see the flick and got a hard time from one of the actors.

“He was merciless,” she says. “He kept asking, ‘who brought them here?’”

A few minutes before midnight, a woman with green streaks through her hair and a jacket with a security patch sewn on stomps into the street and hollers, “If you’re here for Rocky Horror Picture Show, come on in.”

After the line shoves its way through the theater’s doors, this self-appointed head of security orders the crowd to sit down: “Seats are only as good as the butts that are in them.”