Kieran Culkin admits to getting Mark Ruffalo high on stage during their Broadway run of The Moment When

Kieran Culkin is fessing up to a prank he pulled nearly 25 years ago on his one-time Broadway co-star Mark Ruffalo.

The 42-year-old actor was just 17 when he starred in a 2000 production of James Lapine’s The Moment When.

One scene called for Ruffalo to roll and smoke a fake joint, with Culkin revealing there was a ‘bag of fake joints,’ and he swapped one of them out with a real one.

‘I was 17 and stupid,’ Culkin admitted, adding that weeks later, he smelled marijuana and knew the real joint was found, as it turns out, by Ruffalo, on stage.

He added that he ‘just watched’ as Ruffalo took long, extended draws from what he thought was fake weed.

‘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 admitted. 

One scene called for Ruffalo to roll and smoke a fake joint, with Culkin revealing there was a ‘bag of fake joints,’ and he swapped one of them out with a real one

‘Mark says, “I haven’t smoked pot in 10 years; the second half’s going to be so much fun,”‘ Culkin added.

He said there was another co-star, ‘who had never smoked pot in her life,’ who said,  ‘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,”‘ Culkin said, though admitting the stage manager was not as happy.  

‘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,”‘ he recalled.

‘I sheepishly handed her the roach and she said, “Ruin your life on your own time,”‘ Culkin added.

Ruffalo previously spoke about the incident back in 2012 during an appearance on The Graham Norton Show, though he didn’t identify Culkin as the culprit.

‘There was a play that I did that I had to smoke a joint in the first scene. 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,’ Ruffalo said.

He admitting that he tends to ‘overdo everything’ when he’s performing on stage, explaining he was taking in very large inhales of what he thought was fake weed. 

‘Mark says, “I haven’t smoked pot in 10 years; the second half’s going to be so much fun,”‘ Culkin added

He said there was another co-star, ‘who had never smoked pot in her life,’ who said, ‘Is this what being high is? This is lovely’

‘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,”‘ he recalled

‘And the kid who put the joint on the prop table is standing there, [laughing]. And I just went, “Oh s**t,’ he said

‘Between the two of us, we smoked a giant blunt on stage. And I’m like, “Man, I am in it tonight. I feel it. I’m on fire. I’m feeling it… why’s that dude standing backstage laughing at me?”‘ Ruffalo said.

‘And the kid who put the joint on the prop table is standing there, [laughing]. And I just went, “Oh s**t,’ he said.

‘But at the end of the play, I got the best reviews of my entire career,’ Ruffalo said, though he admitted it was a ‘nightmare experience’ and he would ‘never do that again.’

Culkin is currently earning rave reviews for his performance in A Real Pain and he will be returning to Broadway this spring in a revival of Glengarry Glen Ross.