Kieran Culkin has revealed that a director branded him as 'stupid' during his first ever acting job when he was just six years old.
The former child star, now 42, had been shooting a commercial for 'something to do with learning disabilities,' when things went awry on set.
During the commercial, he was playing a kid who couldn't solve an 'easy' problem at school.
His classmates were supposed to make fun of him for it, but when the director began calling him names, Kieran was left horrified.
Speaking to Jason Bateman, Sean Hayes, and Will Arnett on the latest episode of the Smartless podcast, Kieran opened up about the traumatic experience.
He said: 'The concept was, I'm standing in front of a chalkboard with chalk in my hand and I don't know how to solve the easy thing in front of me.
'And the kids in the class are supposed to be calling me a dummy and stupid, all that.
'I have a distinct memory of being there and the director going, "OK, action." And he starts going, "Dummy. Idiot. Stupid."'
Kieran Culkin has revealed that a director branded him as 'stupid' during his first ever acting job when he was just six years old. He's seen earlier this month
The former child star, now 42, had been shooting a commercial for 'something to do with learning disabilities,' when things went awry on set. He's seen with his brother in 1990
The anecdote left the podcast hosts shocked, with Kieran going on to note that even at six years old, he realized that it was an odd move from the director.
He added: 'I'm thinking like, "I get it. I'm six. Stand here and look sad. I'm not f***ing method [acting]. I'm six. What's wrong with you?"'
He didn't reveal who the director was.
Following his role in the commercial, Kieran starred alongside his older brother Macaulay Culkin in the 1990 Christmas film Home Alone and the 1992 sequel, Home Alone 2: Lost in New York.
While Macaulay led the cast as the precocious Kevin McAllister, Kieran, who was then seven, had a small supporting part as Kevin's bedwetting cousin Fuller.
His other early acting credits included 1991's Father of the Bride and 1995's Father of the Bride Part II.
In 1991, Kieran also appeared on Saturday Night Live when his brother Macaulay hosted.
Kieran has been married to his wife Jazz Charton since 2013 and together, they share two children - a daughter called Kinsey, five, and a son called Wilder, three.
During the commercial, he was supposed to play a kid who couldn't solve an 'easy' problem at school. But when the director began calling him names, Kieran (front left) was left horrified
Kieran didn't name the director who called him an 'idiot' when he was a child
Earlier this month, he revealed why he has not allowed his children to watch Home Alone.
'There's still some scary parts,' Kieran told E! News at The Gothams 34th Annual Film Awards in New York City.
'For the three-year-old, there's the tarantula [and] there's the guy at the end who said, "I'm gonna bite off all your fingers."
'That's scary for a three-year-old.'
However, Kieran added that the time for a change may be right around the corner, teasing: 'We think they might be ready for Home Alone this year. If not, next year.'