Luffy’s traits of a D.

As a person with the middle initial D., Luffy shares the common trait of not fearing death. He will often state that if he reaches his goal, that’s fine, but if he dies on the way, that’s fine too. He even smiled when he was nearly executed by Buggy in Loguetown, although he did have a look of shock and surprise in his eyes before this happened when Sanji and Zoro tried to rescue him.

Throughout the series, several characters have stated similarities between Luffy and other D. carriers, whether in personality, words, actions or presence. So far he is thought to be similar to Jaguar D. Saul by Robin; to Monkey D. Garp by Aokiji, by at least one of the Gorosei, and by his own crew; to Monkey D. Dragon by Emporio Ivankov; and to Gol D. Roger by Smoker, Crocus, Kureha, Gan Fall, Shanks, Rayleigh, Kokoro and Shakuyaku. 

Also, after the events of Enies Lobby, Luffy seems to have developed narcolepsy, much like his brother Portgas D. Ace, though for only a short time.

Like other D’s so far, he is also an immense glutton despite his skinny appearance: he especially loves meat and can eat a fish whole – bones included – and because of this, a running gag of Luffy’s is him constantly stealing other peoples’ food with his rubber powers, causing them to yell at him and sometimes hit him. Due to his gluttony, Luffy can end up losing control in times of dire hunger. When he expended all the crew’s food supply while on the way to Whole Cake Island, he was thinking about using Chopper as emergency food ration and in the anime, he tried to devour Chopper alive twice and had to be beaten by Nami.