Douglas Carter Beane picked a bad movie to adapt into a musical.

“You should underline ‘bad’ and put it in boldface,” says the playwright, when describing the 1980 film “Xanadu.”

The flop film stars Olivia Newton-John as a Greek muse who helps a struggling artist open his dream roller disco. People assumed that Beane’s musical version of the story would be equally lame.

“It was a wonderful, subversive way to make fun of theater’s current infatuation with movie titles,” Beane explains of his rationale. “And the original score was great. The soundtrack was a huge seller.”

So Beane saved the score and gutted the rest from the first “Xanadu.”

“I think at the end of the day, there are only seven lines from the movie that we kept. I completely restructured the entire story,” the writer says. His musical elaborates on Greek mythology and includes a few parody nods to the movie.

On Broadway, the show proved the skeptics wrong: It earned positive reviews and four Tony Award nominations.

“At the end of the day, ‘Xanadu’ is a toxic brand. People love it. This demigod of inspiration comes in the year 1980 to help open a roller disco. To a comedy writer, that’s just gold,” Beane says. “I took this terrible art form, this second-rate cinema, threw it up on stage, and called it a show.”

Beane there, done that

Douglas Carter Beane has been busy: He just received a Tony nomination for his most recent musical, “Lysistrata Jones” (like “Xanadu,” the show has some ancient Greek roots). He’s also reworking “Cinderella” for Broadway in 2013.