
Thank you for asking! Rubin is played by Crispin Glover, the actor who played George McFly from Back to the Future. He dressed up as this character to troll David Letterman who was known to make fun of his guests instead of talking about their careers. He was the first and only person ever kicked off that talk show in all its existence. But they invited him back as Letterman realized he overreacted (Glover “kicked” by Letterman’s head as a reference in the movie and
Letterman didn’t like the fact he was taking control over the show), and in his third appearance, Glover was asked about the kick again as a way of Letterman trying to get an apology, so Glover takes control over the conversation by pivoting to the Rubin and Ed movie. He acted as though he’d met Rubin in school during an eclipse, and that he looked exactly like him. Letterman cut him off before he could explain that it wasn’t him on the first appearance of this show, but rather Rubin
…who was ultimately played by Glover in the movie, so it was him. But he’s acting as though they’re two separate entities. He just does some high level trolling which does take a minute to put the puzzle pieces together after watching his interviews. They’re really not that long of interviews though, especially the one he was kicked off of lol. Definitely recommend doing a deep dive and witnessing his epic personality