The 28-year-old had to bulk up for the part, and Fallon whipped out these pretty great before-and-after photos.
Let's take a closer look 💪
Oooooh yeah.
Fallon also asked Teller about a recent photo shoot in Vanity Fair where he sports some dapper facial hair. Fallon joked: "Are you playing Justin Bieber in a movie?"
Don't mess with Teller's facial hair — it's so delicate and wispy, it belongs in a museum.