Yes, that's Jon Hamm's butt in the 'Your Friends & Neighbors' season 2 premiere

I'm sure the question was on everyone's minds so thank goodness he confirmed it. That's his real deri3rre, folks. We can rest easy now.  ""Speaking of doing all right, in the first six and a half minutes of season 2, we see your butt," Andy Cohen mentioned, before cohost John Hill asked, "Do you have a butt double?" Hamm said he doesn't have one, confirming that it's his "real butt." Cohen and Hill then asked if Hamm prepares his body for any scene that could include his derrière, or if he thinks about his butt being seen. Hill wondered what happens if there's a zit present. "Well, if I do, that gets fixed in post. Come on," Hamm chided. But can it get plumped in post? "That, I don't know," the actor admitted.

Not a first time. He showed his butt pretty prominently in Fargo.