First he reminisced about shooting the iconic opening sequence, which he said took hours and by the end of it "everyone had pruney fingers".
And then he told a behind-the-scenes story about the episode "The One Where No One's Ready" which, of course, we all know well.
It's the episode where Ross is trying to get everyone ready to attend a museum function (typical Ross), but they're all taking too long, and apparently Matt was busy injuring himself.
It was only the second scene of the day, and the audience was full of people who'd won a competition to see the show being filmed, which was a ~big deal~.
Let's take a moment to remind ourselves of the incredibly dangerous and potentially fatal stunt:
Somehow the entire thing went terribly wrong, and Matt ended up dislocating his shoulder.
Ouch.
Of course, the audience just thought it was part of the script.
And meanwhile Matt was backstage, thinking he was hallucinating.
And that's the ~real~ reason why Joey was in a sling for a few episodes of Season 3.
