AppearanceGarp is an old man with a broad chest. He is bearded and has a scar on his left eye. Due to the fact that he had appeared in Romance Dawn V.2 with his face, he wore a dog mask when he was first introduced, so fans would not realize he was Luffy's grandfather. When this fact was revealed he discarded the mask, and hasn't been seen wearing it since.
When he was younger, Garp's hair and beard were still black, but he already had the scar above his left eye.
PersonalityGarp displays an intelligence level that is equivalent to that of Luffy's; however, Garp seems somewhat more absent-minded than his younger grandson. Due to his hot temper, he is unable to accept excuses (and is really poor at creating his own) and at times likes to enforce his point of view on things with his fist.
He also is somewhat of an eccentric person with a rather strange approach to things - Rather than entering through doors, he finds that bursting through walls is the "cooler" thing to do (implying his odd sense of "cool"). He, like his grandsons, has an extreme fondness for food; in his case, especially donuts.
Garp has shown signs of narcolepsy. He is seen in the Post-Enies Lobby arc randomly falling asleep while punching Luffy. Coincidentally Luffy fell asleep at that very same moment, suggesting that narcolepsy may run in the family. It might, however, just be a psychological trait that Luffy picked up, as Garp's adopted grandson Ace showed signs while at a diner during the Arabasta arc.
Garp also has his own laughter style: he adds either "Bwa" or "Wa" before the haha part.
CrewHis crew and others around him often react with shock or uncertainty when hearing his reactions to things. At times he will say things that are random or seems to be unaware of the true extent of what is going on around him. At the Marine HQ, many of the other Marines are afraid of him for his reputation and habit of controlling things through his fists.
He is also the mentor of Koby and Helmeppo, he keeps them out of trouble and ensures they are not slacking off. If they do get out of hand, he knocks them around to ensure they keep in place. They both come to admire him, even though he maintains a highly brutal clutch on them because they wouldn't be where they are without him.
SengokuAs a hero of the marines, Garp has the high respect amongst the marines, even with Fleet Admiral Sengoku. However, currently, as with the revelation that both Monkey D. Luffy and Portgas D. Ace are Garp's grandsons (Ace being adopted), as well as Luffy's multiple actions in such a short time, Sengoku is losing patience with Garp. Garp, on the other hand, seems to merely laugh it off and enjoys getting on Sengoku's nerves. Notably, Sengoku's biggest annoyance is Garp's refusal to keep his family under control even when threatened with the consequences; Garp simply does not believe the life of an old man could ever atone for the actions of his family.
When or how long Sengoku knew of Garp adopting Ace is unknown, but Sengoku found out that Ace is the son of Gol D. Roger. Also, how long Sengoku knew that Luffy and Dragon's family relationship is unknown, but Sengoku had no problem in revealing all of it worldwide. How any of this would affect Garp's standings in the Marines is yet to be seen.
Monkey D. DragonDragon is Garp's son. No direct interactions have been shown, however, he seems casual about the idea of his own son being a revolutionary and wanted by the World Government. Garp denied Luffy and Dragon's relationship from the world in the hopes to protect his grandson, but by the time Sengoku made it public, Garp simply states that titles mean nothing anymore.
Monkey D. LuffyHe seems to hold high standards for his grandson Luffy and gets mad at the slightest mistake he does even when his own are sometimes no better (i.e. telling off Luffy for falling asleep yet falling asleep himself). Even when Luffy was too casual in saying goodbye to Garp at Water 7, Garp was disappointed by a lack of emotion after the two were separated for a long time. This often leads Luffy to be at the other end of Garp's punches and due to this experience he has become afraid of him. Garp also claims Luffy was poisoned by Shanks with ideas of becoming a pirate, as Garp wanted Luffy to be a great Marine like him. However Luffy claims he told Garp even as a child he wanted to be a pirate. Nevertheless the two get along quite well.
As Nami stated at the time of Garp's departure, there seems to be an amazing ego that runs in Garp's family.
Portgas D. AceGarp adopted Ace from Gol D. Roger, who requested Ace does not deserve to be treated as a criminal just because of his family ties. At first thinking of adopting Ace was preposterous idea, Garp eventually agreed to Roger's final wish, as the latter pointed out that after countless confrontations, he trusted the Vice-Admiral much as a friend. Indeed, Garp seemed troubled when Ace was about to face death. While he may be harsh with Ace, he cares about him deeply, openly crying for his grandson as he's about to be executed for being a pirate, angrily asking why he couldn't have just been a Marine. Garp even mentions to Admiral Sengoku that he would have saved Ace if he was able to, and that while he feels no pity for pirates, family is different.
As well as Luffy, Garp had high expectations for Ace to be a strong Marine, but is disappointed that he chose the life of piracy, which incidentally sent him to Impel Down where they were talking about the issue. However, Ace refused the idea that he and his younger brother could have ever been Marines, with their fathers' restless blood in their veins.
Gol D. RogerBack when Gol D. Roger, the great Pirate King, was active, Garp managed to corner him many times. As such, they have a long history against each other. However, when Roger was about to be executed, after turning himself in due to his terminal illness, he made a final request to Garp. He asked Garp to take care of his unborn child, as it didn't deserve to be condemned as a criminal because of his father's crimes.
Due to their countless clashes, Roger came to see Garp as much of a friend as the rest of his crew.
Other PiratesOver his many years as a Marine hero, Garp has made many enemies with pirates over the sea, such as Whitebeard and Shakky. He felt neither remorse nor pity for any of these pirates, as they are criminals.
OtherNo wife has been named for Garp, however the supplement Grand Line Times left a "?" in place of one. Also as a person carrying the Will of D, he may be related somehow to others also carrying it.
Abilities and PowersAlthough rather old, Garp possesses an incredibly-high amount physical strength. He's able to throw iron cannonballs as if they were baseballs and yet still exhibit a cannon-like effect at the point of impact, break through brick walls and cannon stands with his fists, and both carry and throw a gigantic ball and chain many times bigger than the Thousand Sunny. Garp also has a monstrous punching ability at his disposal, with his epithet, "Garp the Fist" vouching for his punch strength. In addition to his legendary strength, he has an extreme amount of endurance and stamina, as seen when he was slashed by Captain Morgan's axe hand and was able to recover only seconds later, with no obvious pain and apparently being oblivious to the fact he was struck at all. He has also shown inhuman speed, as he managed to bypass all of the Straw Hats and Franky in order to get to a sleeping Luffy, appearing as a blur while doing so. He's also a "hero" of the Marines and is known for cornering and fighting Gold Roger many times. Whitebeard seems to respect Garp's strength as he mentioned him during his talk with Shanks. It shoud also be noted that Garp is not seen to carry any weapons, implying he is most likely a hand-to hand fighter
WeaponsSo far he's been seen throwing cannonballs (including a giant one, mounted on a chain) with his bare hands. The cannonballs he threw soared at a faster velocity, then when fired out of a cannon, due to Garp's strength. An interesting fact is that Garp is one of the few people with the initial D. to use materialistic weapons.
Attack List* Fist of Love (愛の拳, Ai no Kobushi): A simple but powerful punch to Luffy's head, strong enough to hurt the rubber man heavily. It's a gag technique to show his "love" for his grandson.
* Iron Fist Meteor (拳・骨・隕石, Gen Kotsu Meteo): Garp throws a cannonball at an enemy ship. Due to Garp's Super-Human Strength, he can throw them like baseballs, and the impacts are more powerful then when being fired from an actual cannon.
* Iron Fist Meteor Shower (拳骨流星群, Genkotsu Ryūseigun): Garp throws 1000 iron cannonballs at enemy ships. The cannonballs are supplied by conveyor belts either side of him.