Kieran Culkin admits to getting Mark Ruffalo high in stage prank, says he was young and 'stupid'

LOS ANGELES, CALIFORNIA: Kieran Culkin recalled a mischievous incident during the opening night of the 2000 play 'The Moment When'.

In an interview with The Guardian, Culkin revealed he swapped a prop joint with real marijuana, unwittingly leaving co-star Mark Ruffalo and others on stage genuinely high.

Kieran Culkin on regretting his decision to pull the prank

Speaking about the prank, Kieran Culkin admitted, “I thought this was a good prank. I’m stupid."

"Oh my God, I’m so sorry.' But actually, they loved it," said the 'Succession' alum.

The joke initially backfired when Culkin was hit with the smell of weed mid-performance, prompting immediate regret.

However, his co-stars took it in stride. Ruffalo, who had abstained from marijuana for a decade, reportedly quipped, "Mark says, 'I haven’t smoked pot in 10 years; the second half’s going to be so much fun.”

Mixed reactions from the cast and crew

Other actors, including Phyllis Newman, reacted lightheartedly, with Newman humorously thanking Kieran Culkin and reminiscing about her last experience of smoking pot in the 1960s.

Still, not everyone was amused. The stage manager sternly reprimanded Culkin, saying, "I don’t care whose it is, or what happened, but Kieran, give me the joint." 

Confiscating the joint with a warning, the stage manager said, “Ruin your life on your own time.”

Years later, while performing 'This Is Our Youth' in London’s West End with Colin Hanks, Culkin joked about repeating the prank.

Hanks initially threatened to punch him if he tried, but by the end of the run, he relented.

Culkin once again handed over real marijuana, causing Hanks to nervously fumble with the joint on stage. Luckily, a fake prop joint saved the performance.

Mark Ruffalo’s side of the prank story

Mark Ruffalo recalled the incident during a 2020 appearance on 'The Graham Norton Show', though he refrained from naming Kieran Culkin as the culprit.

Ruffalo explained how stage acting’s exaggerated gestures led him to dramatically puff the real joint, unwittingly amplifying the effect.

"I’m like, ‘Man, I am in it tonight, feeling it,’” Ruffalo joked, adding that the prank left his inexperienced co-star hilariously baffled.

While he condemned the stunt, Ruffalo acknowledged it resulted in “the best reviews” of his career.

Culkin, now 42, assured audiences his pranking days are over.

“I’m not going to try to get anyone high on stage,” he shared, according to People.

Reflecting on his youthful antics, he summed it up with a simple admission, “I was 17 and stupid.”