At a young age Luffy is befriended by a pirate named Shanks
. Luffy wants to go on adventures with Shanks on his pirate ship, but Shanks believes that Luffy is too young. One day a bandit makes a fool of Shanks in a local bar and Shanks just laughs it off. Luffy is very disappointed in the way Shanks responded to the confrontation and walks away with disgust. A couple of days later Luffy bumps into the bandit, who is making fun of Shanks. Luffy tries to teach the bandits a lesson but ends up on the wrong side. Eventually Shanks and his crew comes to aid Luffy. Though, the leader of the bandit escapes with Luffy on a boat in where a Sea King attacks them. Shanks saves Luffy at the last second but loses an arm in the process. Shanks leaves Luffy after the ordeal but gives Luffy his straw hat as a token of their friendship. When Luffy receives the hat, he proclaims that he will become the greatest pirate in the world.
Luffy got his powers when he ate the Gomu-Gomu (lit: "Rubber-Rubber") Devil Fruit. The fruit turned his body into rubber allowing him to stretch and expand any part of his body. Most of his attack moves work like an elastic band so when he stretches his arm, it springs forward with incredible force. Luffy is also able to pump up his body with elastic pumps that allow him to increase his blood pressure and do more devestating attacks. The downside for everyone who eats a Devil Fruit is that they can't swim and sink in the water like a hammer.