Kieran Culkin Reveals He Pranked Mark Ruffalo with a Real Joint on Stage

Kieran Culkin has confessed to a mischievous act from his youth, revealing that he swapped a prop joint for a real one spiked with marijuana while performing in a stage production with Mark Ruffalo in 2000. At the time, Culkin was 17 and thought it would be a good prank, though he now admits, “I’m stupid.”

In an interview with The Guardian, Culkin recalled how Ruffalo, who had been sober for years, and their co-stars unknowingly smoked the real joint during the play.

Ruffalo later joked about how much fun the second half of the performance was, while other cast members, including Phyllis Newman, enjoyed the unexpected high.

The incident occurred during their production of The Moment When at Playwrights Horizons. Culkin recalled how the stage manager intervened, demanding he hand over the joint, and later told him, “Ruin your life on your own time.”

Though Ruffalo had previously mentioned the prank on The Graham Norton Show, he kept Culkin’s identity secret at the time. Culkin, now 42, says he’s learned from the mistake and would never pull such a stunt again.

Currently, Culkin is promoting A Real Pain, a road comedy directed by Jesse Eisenberg, where he has earned a Golden Globe nomination for his supporting role.