Matthew Perry can't remember filming several years of Friends, due to his substance abuse.
The actor opened up in an interview with BBC Radio 2, admitting the filming blackout, after he was asked which episode was his least favourite.
"Oh my goodness. I think the answer is I don't remember three years of it. So none of those … somewhere between season three and six...a little bit of the time, I was a little out of it, yeah," he said.
The 46-year-old has been open in the past, speaking at length about his struggle with sobriety.
In an interview with People in 2013, he admitted to abusing alcohol and prescription medication before getting clean.
"I was a hopelessly narcissistic guy, and I only thought about myself, and then that just shifted. And when that happened, I got some true happiness and comfort in my life."
Perry is set to star in a play called The End of Longing, debuting in London in February.
This was the role which kept him too busy to attend the reunion of his Friends castmates at the taping of NBC's tribute to James Burrows, but he is expected to make an appearance via video when the special airs on February 21.
However, the remaining Friends, Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc and David Schwimmer have all reunited for the upcoming special.
They even snapped an Instagram pic with the cast of The Big Bang Theory; Kaley Cuoco, Johnny Galecki, Simon Helberg and Jim Parsons, which Cuoco posted with the caption: "Um, night made. Can't breathe...I died and went to heaven".