"Straw Hat Pirates" has been featured, meaning it was chosen as an article of interest.
In the beginning of the manga, Luffy claimed that he wanted at least ten people to join his crew before entering the Grand Line (not counting himself).[13] This was changed after Usopp had told Luffy that after "the chef" joined them, they would rescue Nami and go to the Grand Line.
Although this is long past the expiration date, it can still serve as evidence that there will be at least ten Straw Hats at one point of the manga (excluding Luffy himself). Luffy also claimed in the beginning of the manga, that he would gather a crew strong enough to surpass his childhood hero Red-Haired Shanks.[14]
Usually when he asks someone to join, Luffy is turned down completely; though the way of which he is turned down varies. Luffy never forces people to join his crew against their will. When Luffy asked Brook during the Thriller Bark Arc, Brook said yes immediately. Luffy did not directly ask Usopp to join the Straw Hats, however when Luffy, Zoro and Nami were about to sail off, Luffy assumed that Usopp would join them as they had just fought off Kuro. The only exception was Franky who was stated to be too stubborn to ever accept joining Luffy willingly (his swim briefs had to be stolen just to lead him back to the Straw Hat Pirates), but ends up joining willingly anyway after being moved by Iceburg's words.
However, if the person interests Luffy very much, he will still try to get them to join anyway regardless of their initial decision. While most people turn down Luffy's offer regardless of how hard he tries, only those convinced enough will join for reasons of their own. However, even if he is rejected, Luffy will treat the person as if they were already a crew member, much to their annoyance. He will sometimes act as if it is his decision and not theirs whether they join or not (though it is worth noting that when Luffy's decided someone is joining, they do eventually join). Although, when he tried to recruit Kureha to be their doctor, she refused.
The major exceptions to this rule are Usopp, who was thrilled to be asked to join and accepted immediately, and Nico Robin, who invited herself into the crew and had to convince the crew to let her stay. Also notable was Brook, who actually accepted Luffy's initial invitation to join the crew, but later claimed that he could not honor it due to his lack of a shadow, which would result in his death should he step into sunlight, as well as unfinished business with the zombies of Thriller Bark. However, after the Straw Hats and Brook finally defeated the zombies, Brook later asked if they would honor his initial acceptance and Luffy gladly welcomed him into the crew, though everyone else were shocked by Brook just asking like that. Jinbe also wanted to join after being asked, but he stated he had had unfinished business to do (which was to leave his alliance with the Big Mom Pirates), but did state if they still want him to join after that's done, he will gladly join the Straw Hats. Following Kaidou's defeat, Yamato wanted to join the crew, but Jinbe suggested to wait for Luffy's confirmation of allowing Yamato to join the Straw Hat Pirates. Due to Admiral Ryokugyu's invasion, however, Yamato decided to stay Wano Country to protect it from outside threats instead, though he still desires to join someday.
Luffy does not seem to mind if someone he wants to recruit has a profession or not. He allowed Usopp to join, and later on names him the team's sniper, and considered Vivi and Karoo members even though her only "profession" would be a princess. He also did not know that Chopper was a doctor and wanted him to join for his seven transformation abilities. He also offered Gaimon and several Thriller Barkzombies the chance to join his crew, when they had no apparent usefulness to the crew aside from experience and their uniqueness respectively. Also, when a crew member finally joins, they are often run out of their home by loved ones, mostly out of goodwill to encourage to leave pursue their dreams.
Luffy's tendency to ask people who interest him to join often led him to attempt to recruit bizarre creatures into his crew at a whim (such as Chopper, Brook, Unigaro, MocDonald, and Ashimaro, the latter three never joined the crew eventually), which would annoy the rest of the crew, prompting them to snap at him to stop.
Recruiting Process
Though most adventures in One Piece are random, there seems to be a "process" for recruitment:
First, a situation arises where someone new is needed. The crew comes across someone who fulfills the criteria (i.e., Nami the navigator, Sanji the cook, Chopper the doctor, Franky the shipwright, etc.). Luffy offers the person a position, and is usually turned down initially (which usually causes Luffy to comically "refuse this refusal").
Meanwhile, a situation arises where, some way or another, Luffy ends up battling a 'boss' character, and the would-be crewmate battles an underling (i.e., Luffy vs Don Krieg after Sanji battles Gin and Pearl, and Luffy vs Wapol as Chopper battles Chessmarimo). The would-be crewmate typically defeats one of the villain's henchmen, or otherwise plays a crucial role in the Straw Hats' victory (for example, Brook defeats Tararan and reveals the zombies' weakness, despite losing to Ryuma).
During the arc in which the new crewmate is introduced their backstory and dreams are revealed, (although Nami and Robin's back stories were revealed later) thus convincing them to join the Straw Hat Crew.
Meanwhile, Luffy's current crew would assist him in battling various enemies generally in rank of abilities and overall strength which is matched by whoever they are battling (i.e. Zoro vs Kaku, Sanji vs Jabra, Chopper vs Kumadori, Nami vs Kalifa), the enemies fought also have similar fighting styles (Zoro vs Hatchan who are both swordsmen, Sanji vs Kuroobi who are both martial art experts, and Usopp vs Chew who are both ranged weaponry experts), this is more consistent when it concerns Sanji and Zoro (and later on, Franky, against close combat experts). This process also led many fans to think Vivi would become a permanent crew member, even though she decided to stay in Arabasta and Nico Robin became the new crew member instead.
The only crew members not to follow this process were the female members, Nami and Robin, both of whom never helped fight an enemy during their joining and had their backstories fully revealed later on, despite initially being hinted at. Nami's official recruitment was when Luffy, Zoro, Usopp, and Sanji defeated Arlong and his pirates. Robin was the first to initially willingly join, and then officially joined after the rest of the Straw Hat Pirates had arrived to her rescue from CP9.
Jinbe's recruitment process was quite different, as he officially joined the crew only after several arcs from the first time he fought an enemy alongside the entire crew.
As a side note to this process, Luffy has several times stated the need for a musician,[15] because he believes that "pirates love music" due to him being influenced by Shanks the captain of the Red-Haired Pirates whom are mostly seen singing and partying. As a result, whenever the need for a new crew member arises, Luffy would usually bring up the musician position despite it being completely unrelated to the problem at hand. While Franky plays the ukulele in addition of being a shipwright, Luffy's plea was finally fulfilled when Brook joined the crew.
On the opposite side of the spectrum, when seven groups pledged their allegiance to the crew, Luffy declined as he was disinterested in having a fleet under him. Nevertheless, the group would be collectively known as the Straw Hat Grand Fleet, in which the World Government recognizes them as part of Luffy's expansive crew.
Returning to the Crew
If a Straw Hat crew member leaves the crew without Luffy's permission, Luffy does his best to recruit them back. So far, Nami, Robin, and Usopp have all chosen to leave the crew in the past, before returning. Additionally, Chopper and Sanji have been coerced by third parties to leave the crew despite their wishes, with Chopper returning soon afterwards. The situation with Sanji, however, lasted for around a week.
Nami rejoined after the defeat of Arlong, who blackmailed her into betraying the crew, while Robin rejoined the crew after they convinced her that they would stand by her even if it meant declaring war on the World Government, and saving her from Enies Lobby and probable incarceration at Impel Down. However, while Robin and Nami were never on bad terms with the crew when they left, any suspicion that they had betrayed the Straw Hats was soon proven false.
Usopp was a different case; he had officially left the Straw Hat crew, over a dispute concerning the Going Merry (yet returned to the crew in his alias "Sogeking" to help in the rescue of Nico Robin) and his own insecurities about his strength. Afterward, Usopp originally planned to make the crew beg for him to return, but Zoro had given the crew a stern speech about him rejoining them on their terms, not his, and would accept him only if Usopp begged them after a thorough apology. After being ignored while they were fighting off Garp, Usopp finally apologized, and Luffy happily and tearfully accepted him back into the crew.
After losing the first game of the Davy Back Fight, Chopper was selected by Foxy to join his crew; as part of this, Chopper was required to swear allegiance to his new captain. However, after Zoro and Sanji defeated the Groggy Monsters in the second game, Luffy reclaimed Chopper into the crew.
During the Zou Arc, Sanji disappeared following the revelation of his arranged marriage to Charlotte Pudding. It was explained by Pekoms to Luffy that, if and when the marriage is formalized, Sanji will automatically cease to be a member of the Straw Hats and will become a member of the Big Mom Pirates. However, it turns out to be false, as Big Mom's true intention is to assassinate Sanji and the entire Vinsmoke Family during the ceremony. During the prelude of the marriage, Sanji, under duress, acted thoroughly disrespectful to Luffy and Nami in an attempt to get them to give up on him, though Luffy did not buy it, seeing Sanji's insincerity, and eventually managed to assist him to escape without consequence.
After finding out he is about to be executed by the Marines, Zoro realized his only way to live to achieve his dream of being the world's greatest swordsman was to accept Luffy's help and escape, thus becoming an official pirate and the first crewmate.
While being chased by the Superhuman Domingos, Nami encountered Luffy and, seeing his power, decided to recruit him in her attempt to steal from Buggy. Afterwards, Nami saw the value of a strong protector and Luffy's honor, and decided to travel with the crew with Luffy claiming that she was their navigator. After seeing an image of Arlong, Nami remembered her mission from the past and left the crew, only to be followed by the Straw Hats, who later defeated the Arlong Pirates, thus freeing Nami from her obligation and allowing her to fully became the second crewmate.
Usopp met the Straw Hats and tried to scare them off Gecko Islands, however his lies were uncovered and he soon made friends with them. Learning of the Black Cat Pirates plot, the crew helped Usopp protect Syrup Village and Kaya. Afterwards, Usopp prepared to leave the island, and was quickly invited aboard the Going Merry. Later, as the Going Merry began breaking down from the crew's journey, and Luffy deciding to purchase a new ship, Usopp disputed the decision and declared he was leaving the crew. After the events of the Water 7 Saga, he rejoined the crew as their sniper and third crewmate.
Needing a cook, the crew came to Baratie and met Sanji, who had a similar impossible dream as Luffy. With the defeat of Krieg as a payment for Luffy accidently destroying the restaurant, the two were free to leave to chase their dreams. Much later, Sanji's past caught up to him, and was forced to leave to deal with a family issue, and renounced Luffy's help, distancing him from the crew. Later, feeling truly lost, Sanji returned to Luffy and asked for his forgiveness and help, with Luffy agreeing immediately, as Sanji returned to the crew as their fourth crewmate.
As Nami needed a doctor after coming down with the Five-Day Disease, and being treated by Kureha, Chopper was invited to travel with them, with Luffy and Sanji not even knowing about his medical skills. Despite initially refusing to go to outside world because of his past encounters with humans, Chopper was moved by the crew's acceptance and adventurous spirit, and joined as the crew as their fifth crewmate. During the Davy Back Fight, he was traded out of the crew after losing the first round to the Foxy Pirates and being recruited into their crew, later being recruited again by Luffy after winning the second round.
Without any leads to other poneglyphs, Robin was content to die at the collapsing Tomb of the Kings, but was rescued by Luffy, who she deemed responsible for her life, and started traveling with the crew. During this time, she found a new lead in her quest to learn the true history of the world. Soon after, however, her past and notoriety were discovered, and she left the crew in an attempt to save them from her pursuers, but the crew and their allies went to rescue her and bring back their sixth crewmate.
The leader of a family of thugs, Franky was initially antagonistic towards the Straw Hats, having stolen their money and beaten up Usopp, and the crew retaliated by destroying his headquarters. However, the two groups found a common enemy in CP9, who abducted Franky and Robin. After defeating the agents, Franky used the wood he had bought with the Straw Hats' stolen money and his skills as a former shipwright and built the crew a new ship that he claims could take the crew all the way to the end of their adventure, and joined them to fulfill his dream in seeing and maintaining the ship's journey as their seventh crewmate.
Unlike the rest of the crew, Brook did not refuse Luffy initial invitation, fulfilling Luffy's long search for a musician, but took his acceptance back in order to retrieve his shadow from the Thriller Bark Pirates. In order to help their new friend, and retrieve their own shadows that were taken, the crew engaged in a battle against Gecko Moria. With Zoro defeating the revived corpse of Ryuma, releasing Brook's shadow, the living skeleton rejoined the crew as the eighth crewmate.
Jinbe first met Luffy before he did the rest of the crew, but was inadvertently a key figure in Nami's past. Upon earning her forgiveness and enlisting the crew help in saving Fish-Man Island from a coup, Jinbe was invited to join the crew, but turned the offer down to deal with a personal matter. That matter was later revealed to be his crew'sallegiance to the Big Mom Pirates, which he took back in order to accept the role of the crew helmsman and ninth crewmate.