Josh Hutcherson has recalled the time his great-grandma watched him shoot a racy movie scene.

The I Love LA actor had not realised his family would see him "not fully clothed" when they stopped by for a set visit during shooting for his TV sci-fi series, Futureman.

"I've seen some questionable things over the years that my great-grandma has even seen," Josh, 33, told Variety Magazine on the red carpet at the I Love LA premiere in Los Angeles on Wednesday.

"My great-grandma was on set the day on Future Man that we were shooting an orgy."

While he had invited his great-grandmother to come along and see him on set, Josh explained he had not considered the possibility her excursion would coincide with his re-enactment of such an intimate moment.

"I didn't realise the day she was coming also lined up with the orgy shoot," he said, adding he couldn't have dissuaded her from attending even if he'd tried. "She was coming no matter what. She was going to be there. She's a very supportive great-grandma."

Thankfully, Josh said, his great-grandma took the moment in stride and they were both able to see the funny side.

"It was comedy. It was comedic," he recalled. "I was fully, well, not fully clothed. Grandma was like, 'You know, it's fiction. Very interesting, your job, Joshua'."