Sometimes good things come from bad movies.

Steve Guttenberg began a “lifelong” friendship with Caitlyn (then Bruce) Jenner more than three decades ago while filming the big screen disco disaster “Can’t Stop the Music.”

“[On] my 21st birthday in Massapequa, Long Island at my parents’ house, he was the only one from the film who showed up,” Guttenberg remembers.

Guttenberg, 56, says Jenner picked him up in a sports car, drove him to the party and even stopped at the supermarket to pick up groceries for his mother.

“He helped set everything up with my mom and dad,” the actor says.  

“He went to the basement and helped my father rearrange his gym.  He showed my sister his Olympic medals.  He danced with my grandmother.  He cleaned up the party afterwards.”  

Guttenberg continues, “He was one of the last guys to leave.  I can’t say enough about how much I admire Caitlyn.  I will be a lifelong friend of hers.”

Loyalty runs deep for Guttenberg.  

He enlisted three of his “Police Academy” costars --Michael Winslow, Marion Ramsey and Leslie Easterbrook-- to appear with him in the Syfy horror flick “Lavalantula,” premiering Saturday.

“They said I could cast anybody I wanted,” he says.  “The only [other person] I wanted was G.W. Bailey and they wouldn’t offer him enough money.”

In the B-movie thriller, Guttenberg plays a washed up ‘90s action hero actor who works to save Los Angeles from a giant swarm of lava breathing tarantulas released during an explosion in the Santa Monica Mountains.

“It’s a silly movie,” he admits.

But silly sells on basic cable — a lesson Guttenberg learned the hard way.

Back in 2012, the star of “Short Circuit” and “Three Men and a Baby” politely passed on the lead in the unexpected hit, “Sharknado.”  

The role went to Ian Ziering, who makes a cameo in “Lavalantula” as shark hunter Fin Shepard.

“I just thought it was ridiculous and silly and it wouldn’t work,” he says.  “So was I right or what?”

Gutenberg admits he didn’t think twice about signing on for “Lavalantula.”

“When the Syfy channel came knocking, I opened up the door and I gave them a big dinner,” he jokes. “I massaged them and washed their cars.”

“Lavalantula” premieres July 25 on Syfy.

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