While appearing on Jimmy Kimmel Live alongside John to promote their "Suicide Squad" film, Margot recalled her history with the wrestler-turned-actor.
"I watched WWE when I was growing up," she said. "When I was a kid, I loved the Undertaker, and then obviously when I was a teenager I kind of stopped watching. But then, as a late teen, early 20s, I had a boyfriend who was obsessed with John Cena — so much so that he dressed as John Cena for his 21st birthday, and [he] had a cardboard cutout of John Cena in his bedroom."
For two years, Margot slept "with a life-size cardboard cutout of John Cena in the room," she revealed.
"Sometimes I'd wake up in the middle of the night and [gasp] and then I thought, 'Oh, it's just John Cena, it's okay,' she said.
Being a working actress, Margot wondered if she might cross paths with the actual human version of John.
"And I remember thinking, 'I wonder if now that I'm going to work with John Cena, should I tell him this or is that going to be weird?'" she said. "And I thought, 'I'm just going to keep that to myself. I'm not going to tell him. That'd be a weird way to start our working relationship.' And then five seconds into meeting him, I'm like, 'I used to sleep in a room with a life-size cutout of you.'"
John, Robbie said, was hardly creeped out.
"Now I know that there's very little to weird out this guy," she said as she sat next to John, who was wearing his "Suicide Squad" costume.
"In my defense, I was more than likely wearing jean shorts," John said reassuringly.
To even the odds, Anthony Anderson, who was subbing for Jimmy Kimmel, brought out a life-size cardboard of Robbie's Harley Quinn character.
"You also have to sleep with that for two years to level the playing field," Margot told John.