‘Twilight’s’ Booboo Stewart flaunts his fit physique

The dark-haired, muscular "Twilight" werewolf spotted running in L.A. Monday wasn't Taylor Lautner. Instead, it was 18-year-old Booboo Stewart showing off his fit physique! Stewart, who will reprise his role as Seth in "The Twilight Saga: Breaking Dawn — Part 2," which hits theaters November 16, made working out a priority long before his days on the silver screen. He won the Junior Martial Arts World Championship in 2002 and 2003 — beginning at the ripe old age of 8! "I don't really bring it up, people just find out. I just think it's cool," Stewart told ESPN. "They think it's crazy, it's so crazy to be a world champion so young. I don't know what I really think about it. It's just ... it's a really neat thing to do, so hopefully I can return to it one day."

Stewart's young life also has included time making music. He was signed by Walt Disney Records at 12 as part of a group called T-Squad that toured with Miley Cyrus. Oh, and he's done stunts for movies, such as 2007's "Beowulf" with Angelina Jolie, along with other acting roles.

Despite his impressive resume, I couldn't help but wonder: What's the deal with Stewart's first name? As he explained to "Access Hollywood" in 2010 — you know, when he was so much younger — his real first name is Nils; Booboo was a nickname given to him by his mom when he was little because he used to suck two of his fingers, giving him "a boo boo face."

Well, it's definitely memorable!

More celebrity features on Yahoo!:

Follow omg! on Twitter