Twilight director Catherine Hardwicke recalls having to warn star Robert Pattison that his co-star Kristen Stewart was underage after their audition in her home, which involved a passionate kiss.
Speaking on The Big Hit Show Podcast, Hardwicke explained that Pattinson and Stewart tested their chemistry in 2007 on her own bed.
It was so intense that Pattison, then-21 years old, fell off the bed and concerned her due to Stewart being 17 at the time.
"Rob and Kristen did the audition right here on the bed. They did the kissing scene and he fell off and landed right there on this floor," she said.
"[Rob] walked in and he had his hair dyed black for some play, with these wacky bangs. He was a bit out of shape," she continued. "His shirt was just all messy, and I'm like, 'Oh, OK. OK, let's see how this goes.'"
"Rob and Kristen auditioned on my bed, the kissing scene, Rob was so into it he fell off the bed. I'm like, 'Dude, calm down.' And I'm in there filming with my little video camera, whatever," Hardwicke said.
Hardwicke said Stewart told her she wanted Pattison to play immortal vampire Edward Cullen.
"At the end, Kristen was like, 'It has to be Rob,'" she said on the podcast. "I could tell they had a lot of chemistry, and I'm like, 'Oh my God.' I thought, Kristen was 17. I don't want to get in some illegal things.
"So I remember I told Rob, 'By the way, Kristen is 17. In our country, it's illegal to have a sexual …' And he's like, 'Oh, OK, whatever.'"
It comes as Stewart recently reflected on her "young and stupid" romance with Pattinson.
The Spencer star, 31, looked back on making the blockbuster vampire romance franchise, telling The New Yorker about the moment she laid eyes on Pattinson.
"It was so clear who worked," Stewart told the magazine of doing chemistry tests with potential actors to play Edward to her Bella.
She added that Pattinson had an "intellectual approach that was combined with 'I don't give a f*** about this, but I'm going to make this sing.'"
"I was, like, 'Ugh, same.' And, whatever, we were young and stupid and, not to say that we made it so much better, but that's what it needed, and that's what anybody playing those parts needed to feel," she added.
Stewart also said that Hardwicke was "kind of the perfect person to do a young-adult novel that had these dark romantic elements."
"She had this childlike openness and teenage triggers, and her whole sensibility was that the movie was going to feel horny and overconfident," Stewart added.