To examine the show’s impact, O’Brien traveled around the globe interviewing the likes of Curry (a staple of “Rocky Horror’s” stage and screen adaptations), its producer Lou Adler, and Susan Sarandon and Barry Bostwick, who played virginal couple Brad and Janet in the movie. Linus O’Brien grew up with the show, visiting his dad backstage and on set when the musical was being made into a film. That helped when it came time to interview the many artists who helped shape the production over the years.

“The show was a huge part of my childhood, so when I saw everyone 40 years later, there was a real rapport there,” he says.

“It was a rude awakening. In your mind everybody stays the same age. I still think of us as teenagers.”

“Rocky Horror” was the cool, hip, transgressive show when it first played in London. It maintained its rebel spirit when it transferred across the pond and made the leap to movies, with celebrities like John Lennon and Mick Jagger showing up for the film premiere.

The story of a pair of innocents who get lost on their way home and stumble around an eerie castle where a party is raging scrambled classic genres and put a sex-positive spin on them. It didn’t judge its characters’ kinks and desires; it celebrated them.

“Authoritarianism has taken over,” he says. “It’s a huge disappointment. I weep for America.”

Linus O’Brien agrees with his dad. “You would hope that ‘Rocky’ would be a relic right now,. To have it still be relevant in some ways is sad. But hopefully people can still cling to it and feel seen even if they feel like outsiders.”

“Rocky Horror” outstripped its underground origins, becoming a pop phenome that’s globally embraced.

Made for $1.4 million in 1975, the film was initially dismissed by critics and seemed destined for box office oblivion. However, it became a cult favorite after resonating on college campuses. Over time, people would dress in costume, sing along to the music, and talk back at the screen at rowdy screenings. A midnight movie institution, the film is considered to be the longest-running theatrical release in history. Screenings are still taking place around the country, leading to a gross of more than $170 million worldwide.

“Dad’s probably modest about this, but you know, the songs in ‘Rocky’ are incredibly strong, and that’s one the main reason why it’s lasted this long,” he says. “I mean, if the songs were just half as good as they were, we wouldn’t be talking about ‘Rocky’ now. People wouldn’t go week after week. I personally think that song-wise it’s up there with ‘Grease’ and ‘The Wizard of Oz.’”

“Grease’ was looking back and parodying something, but ‘Rocky’ doesn’t do that. I was more rock ‘n’ roll.”