Jennifer Lawrence Reveals How She Got Her 'X-Men' Co-Stars to Punch Each Other

They might be called the X-Men, but it turns out the roughhousing that went on while filming their latest movie was instigated by an X-Woman.

On Saturday night, Yahoo Movies presented the live red carpet from the world premiere of X-Men: Days of Future Past, and naturally all eyes were on returning star Jennifer Lawrence. The Oscar-winner reprises her role as the blue-skinned, shape-shifting mutant Mystique, and while she gets several highly physical fight scenes in the movie, she admitted that fists were flying off-camera as well.

Lawrence revealed that she was the on-set ringleader of the “circle game” — a schoolyard prank where you hold your thumb an index finger in a circle somewhere below your waist and if you can trick someone into looking down at it you get to punch them in the arm. Lawrence told Yahoo’s Ben Lyons, “I actually brought it to X-Men from Hunger Games. We play it obsessively, and I brought it to these guys. They really liked it.” She added, “And I am the best, thank you for asking.”

[Photos: X-Men: Days of Future Past New York Premiere Red Carpet]

Lawrence’s co-star Hugh Jackman — no stranger to the circle game, himself — said that sort of childish fooling around is just part of the job. He told us, “Acting is like being in high school. Well, let’s make it elementary school.” Jackman did say that with Days of Future Past being his seventh time playing Wolverine (including his cameo in X-Men: First Class), he does feel like the upperclassman on the set. He joked, “I really am the mature one. Even around Ian McKellen and Patrick Stewart, I’m the mature one.”

"There was one moment where I was working with Nick Hoult, who plays Young Beast," Jackman recounted. "First day on set he goes, ‘Man, I’m just tripping.’ I said, ‘What’s that?’ He goes, ‘I used to watch you walk down this very hall when I was eight years old.’ And I’m like, ‘Stop. Stop that story right now.’"

[Related: Jennifer Lawrence Unleashes Her Mutant Fury in X-Men: Days of Future Past]

Hoult, who also is Lawrence’s off-screen boyfriend, told Yahoo at the premiere that the violence on set escalated beyond fisticuffs into the realm of firearms. Or, at least, to BB guns. “Me and James [McAvoy] went and bought everyone BB guns and goggles, because it’s very dangerous on the old eyes.”

Hoult said that McAvoy, who once again plays the young Professor X, apparently retained his marksmanship skills from playing an assassin in “Wanted.” Hoult remarked, “I’ve got to say, he’s a little ninja… He was on the fridge, he was jumping on the stairs, pulling himself up. I’ve never seen anything like it.”

"We had to stop eventually," Hoult admitted, "because Josh Helman [who plays Maj. Striker in the film] got shot in the face and he bled." After that, the cast restrained themselves to activities that wouldn’t break the skin.

[Related: How Jennifer Lawrence’s Easier X-Men Costume Might Lead to Mystique Spinoff]

Lawrence has more arm punching in her future, since she said she’ll soon be returning to Paris to continue work on the final installment of the Hunger Games series, Mockingjay. She told Yahoo that her physical training for the action scenes in Days of Future Past was similar to how she prepped to play Katniss with one exception. Lawrence said, “The only thing that’s different from Hunger Games to X-Men is that Mystique moves differently. She moves very snake-like. That was a lot of yoga and learning to move the exact opposite of how I carry my body.”

So she moves differently, but she punches just the same.

X-Men: Days of Future Past opens nationwide on May 23.

Kara Warner contributed to this report.