Kieran Culkin Admits to Getting Mark Ruffalo High on Stage After Swapping Prop Joint for Real One

Kieran Culkin is coming clean about the prank he played on Mark Ruffalo 25 years ago. The A Real Pain actor, 42, revealed in a recent interview with The Guardian that he got the Poor Things star, 57, high while they were in a play together by swapping a prop joint for a real one.

Culkin said he was “17 and stupid” when he swapped the joint out on the opening night of the 2000 production of James Lapine’s play The Moment When also starring Ruffalo and Tony winner Phyllis Newman.

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After the Golden Globe winner smelled weed, however, he immediately regretted what he had done and spilled the beans to Ruffalo. “I’m like, ‘I thought this was a good prank. I’m stupid. Oh my God, I’m so sorry.’ But actually, they loved it,” Culkin told the outlet. “Mark says, ‘I haven’t smoked pot in 10 years; the second half’s going to be so much fun.’ There was this other actor who had never smoked pot in her life. She goes, ‘Is this what being high is? This is lovely.’ And then Phyllis Newman comes in and goes, ‘I haven’t smoked pot since the 1960s. Thank you, darling.’”

Others didn’t find the prank as charming. “Then the stage manager comes stomping in and goes, ‘I don’t care whose it is, or what happened, but Kieran, give me the joint. I sheepishly handed her the roach and she said, ‘Ruin your life on your own time,’” he recalled.

The Succession star revealed that years later when he was doing Kenneth Lonergan’s play This Is Our Youth in London’s West End with Colin Hanks, he joked about pulling the same stunt. But Hanks responded, “Are you f—ing kidding me? If you ever do something like that, I swear to God, I’m going to punch you in the face.”

“But then towards the end of the run, I said it again and he shrugged like he was saying, ‘If you do, it might be fun,’” Culkin continued. “The thing is, his character has to roll the joint every night on stage. So, one day I hand him the real pot on stage and I see him, like, react. It looked like he was excited. But then he got too excited and got nervous. And his hands started shaking so much that he couldn’t get the joint rolled, and when he tried to light it, it fell apart. Thankfully, we had a pre-rolled fake joint behind him, so we ended up with that.”

Culkin noted that all these years later, he does “know better” and is “not going to try to get anyone high on stage.”

Ruffalo previously told the story of Culkin’s prank on The Graham Norton Show in 2020 but didn’t name his co-star as the prankster. “There was a play that I did where I had to smoke a joint in the first scene,” the 13 Going on 30 star said. “And of course, there was a very naughty young actor I was in the play with, who on the opening night with all the critics, he slipped a real joint onto the prop table.”

“We smoked a giant blunt on stage,” he recalled. “I’m like, ‘Man, I am in it tonight, feeling it.’” When he turned around and saw “the kid who put the joint on the prop table” laughing, he knew he’d been had. “It was the worst thing I ever did. Don’t do it,” Ruffalo said, “but at the end of the play, I got the best reviews of my entire career.”