So, I watch the whole episode, because I like Jimmy Fallon, and when I get to the ~20 min mark, I become so confused...
...until I realized Jonah Hill is not a Jonas Brother. I'm so stupid sometimes. Especially with the weight loss, I had no clue, and I'm just staring at the screen going, "Who the F is that? I thought it was a Jonas Brother?" Was watching at work, so I didn't really hear the intro as I'm semi-distracted. Had to come back to this thread to see "Jonah Hill" not "so&so Jonas".
Google is my friend. Found pics, brought myself up to speed and had a good laugh at myself.