Culkin is famous for his role as sarcastic younger Roy son Roman, but he almost missed out on the part as when he asked to audition for it instead he was told that it wasn't being cast yet.
The actor explained to The Tonight Show with Jimmy Fallon how he had decided Cousin Greg, now played by Nicholas Braun, wasn't right for him but that Roman had caught his eye further into the scripts.
He said: "They wanted me to read for Cousin Greg, which I just didn't feel right for.
"They asked me to read for Greg and I knew I was wrong, and normally in any other script, I would be like, 'Okay I'm not right for the part I'm going to close it. I'm not going to continue reading on.'
"But I just kind of liked the script so I read on and I was like, 'Oh, there's this guy.'"
Acknowledging that Braun was the perfect casting as Cousin Greg, Culkin told how he had immediately been drawn to Roman, admitting "I kind of like this guy, I like the way he talks".
Saying that he had asked to audition for Roman instead, he added: "The response back was 'We're not auditioning for that part yet.'
"But I just sort of put myself on tape anyway and sent it in. I was like, 'Here's three scenes if you want to look at this.'"
Of course, it paid off as Culkin was cast as Roman alongside Jeremy Strong, Sarah Snook and Alan Ruck as siblings Kendall, Shiv and Connor, and Brian Cox as their tyrannical father Logan.
The series follows the hugely wealthy but dysfunctional family and their internal power struggles at the top of media company Waystar and is currently airing series three, with series four recently confirmed.
Succession airs on Mondays at 9pm on Sky and is also available on demand on NOW
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