In a new interview with Grantland, Iron Man star Robert Downey Jr. reveals some details about recruiting Steely Dan to perform at his 50th birthday party as well as his love for the group.

“I still only have vague recollections of it,” Downey Jr. says of the party. “Because it was such a mind-blowing affair to see. I can’t even describe my affinity for Steely Dan, Fagen and [Walter] Becker, and each and every person that’s ever played on any of their albums.”

He went on to add, “There’s nothing like seeing Becker verbally improvise along something, where you go, ‘I know they’re going to go back into the song; I know they’re going to hit that beat,’ and it’s so cool. And also when Fagen walks out after the band is kind of prepped, just by playing level-11 jazz fusion, you’re just like, “Oh my god.” And then he steps out and sits down at his electric keyboard. I also noticed, too, that when you’re that … there are people who want to be hip and want to be cool. And then there are people who have ceased any attachment to that and yet they are so, to their core, that.”