A huge part of Jacob’s storyline in the “Twilight” saga is that when he reappears in “New Moon,” he’s much more grown up and has put on quite a lot of muscle … which, it’s later revealed, is partly because his body is about to undergo a dramatic transformation. Bella ultimately learns that Jacob comes from a long line of shapeshifters and that he can turn into a large and similarly muscular wolf.
Lautner was aware of Jacob’s storyline, which is why he started working out hard after the first film. “I knew if I was going to continue playing him, I’d need to,” he told Alex Cooper. “When my team got the call they said ‘Have you seen him recently?’ and they said ‘No, why?’ and my team said ‘You might want to take a meeting with him or something.'” Lautner had gotten incredibly ripped to portray Jacob; thanks to his commitment and hard work, he secured the role for the remainder of the series, becoming a pivotal character and forcing fans to choose between Team Jacob and Team Edward.