A series with as many characters as One Piece has of course produced a few that became unexpectedly popular.
- The reason that Portgas D. Ace got more screentime in the anime than in the manga (in the manga he never traveled with the Straw Hats) was that he became so popular with the fans, even though he only appeared in a grand total of about two-three chapters. Oda has even written a series of novels focusing on Ace.
- Pandaman started out as an Easter Egg-type character that would just show up in the background, and was so popular with the fans that he ended up with his own pirate crew and bounty.
- The polls have shown that Kaku has reached this status, being the most popular character outside of the crew and Ace (9th overall). It is difficult to explain why without ruining some very wonderful surprises in the Enies Lobby arc, so let's just say he's a particularly good example of The Comically Serious and leave it at that.
- The popularity polls have also placed Dracule Mihawk as high as eighth when he hasn't done a whole lot between the Baratie arc and his appearance during the Impel Down and Marineford arcs.
- Crocodile is quite possibly the most popular villain in the series, which may or may not have had something to do with his return to the main story in Impel Down. As an ally of all things.
- Cool Old Guy Silvers Rayleigh, who appeared for a grand total of three chapters and had a fight which lasted about twenty seconds in the arc he was introduced in, yet is overly popular.
- Out of the Admirals, Kizaru is most eligible for this trope, his Story-Breaker Power Light 'em Up Devil Fruit combined with a casually laid-back attitude makes him a fan favourite.
- Trafalgar Law, who appeared in the same arc as the aforementioned Rayleigh and got even less screentime until Punk Hazard and beyond, ranked above Usopp, Franky, and Brook in terms of popularity in Japan, and is quite popular in the West as well. Once he began to play a larger part in the story, he came in second in the fifth popularity poll behind Luffy, overtaking even Zoro (who held the #2 spot in every previous poll), meaning he's become a Breakout Character.
- Boa Hancock, ranked the tenth most popular character, the second most popular female character (Nami being the first), the most popular of the Shichibukai and the fifth most popular "non-Straw Hat" character of the series despite having no major appearance since the short Straw Hat Reunion Arc immediately after the time-skip. Her popularity us such that she was the deuteragonist of the 3D2Y TV special and later the Carbonic Acid King tie in arc to the movie One Piece Film: Stampede.
- Monkey D. Dragon has only made a few appearances so far, but the fact that he's Luffy's father and possibly the single most mysterious character in the whole series means that brains explode basically every time he shows up.
- There's also Mr. 2 Bon Kurei, or Bentham, whose hilarious mannerisms and gigantic heart have earned him the admiration of more or less the entire fanbase.
- Emporio Ivankov is also quite popular among some fans for much the same reasons as Bentham.
- God of Pirates, Buggy D. Clown. Boy is he ever one. His combination of cleverness, skills, and cunning has got him massive darkhorse status, and managing to talk himself into a cushy position as one of the Seven Warlords of the Sea post Time Skip cemented it forever. And then him becoming one of the Four Emperors afterwards immortalized it.
- Caesar Clown is a shining example of Unpopular Popular Character, as while he's rightly despised for his crimes In-Universe, he’s just so damn charismatic and pulls the most epic faces that fans (particularly western ones) can’t help but adore Caesar. Seriously Caesar’s chemistry with the Straw Hats was so fun in Zou that a good percentage of fans actually hoped he’d join the crew or become ally at the very least... despite the fact Caesar experiment on innocent children and even killed some only a few arcs ago.
- While the villains of the Fish-Man Island arc weren't well liked, there is a big exception with Zeo, a member of the arc's Quirky Miniboss Squad and a really good example of a Comically Serious character with hilarious I Meant to Do That tendencies, who is loved even by those who disliked the New Fish-man Pirates.
- Despite only properly appearing for seven chapters as a Posthumous Character in a flashback, Donquixote Rocinante, a.k.a. "Corazon" or "Cora-san", was an instant hit with the fandom due to his memorable design and goofy smile, his endearing level of clumsiness, having an interesting backstory of being a former World Noble who was persecuted for it (similar to his brother Doflamingo's, but more sympathetic in that Roci grew up to be a kind and altruistic man) and is interested in the Will of D, and most of all, serving as a kind and compassionate mentor to the also-extremely-popular Law, being the one who saved Law's life and caused him to change for the better. He has ranked in the top 20 in both character polls taken since he properly appeared (16th in the 6th poll, 13th in the 7th), ranking higher than half of the Straw Hats in the worldwide poll and making him easily the most popular flashback-only character in the series.
- Senor Pink was a minor villain in the Dressrosa arc with his peculiar style of attire juxtaposed with his serious personality baffled a lot of fans, at first. The reveal of his backstory which detailed the love he has for his wife and child and the heartbreaking reason for his attire earned him a lot of respect among the fandom. His manly fight with Franky also helps a lot. Hard boiled, indeed.
- Among the Straw Hat Grand Fleet, Cavendish is quite well-liked. Male fans like him because he's a ridiculous over-the-top parody of the bishonen Long-Haired Pretty Boy stereotype, and female fans like him because, well...he's a bishonen Long-Haired Pretty Boy stereotype.
- Bartolomeo of the Straw Hat Grand Fleet is absolutely beloved for being an Affectionate Parody of diehard One Piece fans. Similar to Cavendish above him, he is widely considered one of the highlights of the Dressrosa arc for his chemistry with the crew and his surprisingly broken devil fruit ability. He even ended up ranking ninth in the 5th popularity poll.
- The most popular newcomers from the Zou arc seem to be Nekomamushi and Carrot, him for his Undying Loyalty and her for her combination of cuteness and badassery, not to mention her good chemistry with the Straw Hats. Carrot’s Badass (not to mention hot and beautiful) Sulong form and the badass beatdown she gave to the Big Mom pirates only made her even more popular, with many fans wishing that she would join Luffy’s crew and become a Straw Hat Pirate herself (which was seemingly shot down due to her new duties as the Mink Tribe's new king).
- Carrot got so popular she ended up in 8th place of the first worldwide popularity poll thanks to voters outside of Japan. Even Oda himself was surprised by her placement.
- Captain Smoker is among the most popular of the Marines for playing the Garp to Luffy's Roger and being one of the most reasonable among their ranks. The fact that he goes everywhere sans a shirt can't hurt.
- A unique Love to Hate example similar to Crocodile, would be Akainu, previously a one note Vice-Admiral who had a notable action of exterminating a civilian ship with the possibility of there being a scholar on there, as well as the Admiral with the least screen time. Cue the Marineford arc, his overall badassness, Determinator tendencies, control over the power of the magma Devil Fruit and his choice of words that led to Ace's death, breaking the long standing rule of "No one important dies outside of flashbacks" has caused him to become one of the top enemies Luffy wants to defeat and notable villains in the series just based on his overall role in the arc.
- Vinsmoke Reiju, Sanji’s older sister, exploded in popularity as she debuted thanks in no small part to her sexiness, caring personality, and unique powers. Seriously, as far the popularity polls go, Reiju is one of the most popular characters introduced in the New World, her Fan Nick Name is “Baeju”.
- "Big News" Morgans, a fairly minor character from the Whole Cake Island arc, gained a ton of popularity as soon as he came in, thanks to his boundless enthusiasm for snagging the "Big News" that give him his nickname, and generally because he's an Intrepid Reporter-slash-mob boss that's also a bird-man (looking rather like Big Bird's deranged cousin) for no conceivable reason (later revealed to be the Bird-Bird Fruit, Model: Albatross). It's all just too absurd not to appreciate. His popularity grew even further when he punched out a Cipher Pol agent attempting to cover up a BIG NEWS story.
- Morgans would probably be even more popular if he didn’t appear in the same arc as Charlotte Katakuri, a character who's the equivalent to a homerun on Oda’s part as he hits all the right bases. For the guys, Katakuri is a supremely badass-designed powerhouse; for the ladies, Katakuri is a sympathetic protective Hunk (if you can look past his fangs) who cares deeply for his siblings and has a tragic back story. Above all, Katakuri flips the rulebook on how antagonists should act as he does the unthinkable and gives Luffy a fighting chance out of pure Villain Respect. Western fans were particularly disappointed Katakuri was only 45th in the character poll (compare it to this poll
, where he placed 6th, ahead of all but three of the Straw Hats, fellow darkhorses like Carrot and Ace, and every other villain).- He placed 14th in the Worldwide Popularity Poll, right behind the above mentioned Donquixote Rocinante, making him the most popular antagonist for now.
- Queen "the Plague" has become a very popular character within the Beasts Pirates in the Wano arc, primarily for his energetic personality, hilarious gags and reaction faces, and pride in his own appearance and quirks. His love of bombastic dance routines and putting on a killer show combined with his highly animated attitude captured a lot of fans' attention. In addition, he shows on several occasions that he deserves his high rank in Kaido's crew through his nonchalant reaction to an attempted strike from Luffy, his absolutely massive Zoan transformation, and his completely insane endeavour to control the rampaging Big Mom involving a diving headbutt off a cliff while in his Brachiosaurus form. His lively opening of the Fire Festival later in the arc only increased his fun factor among fans as well, especially when contrasted with the more grim Lead Performers, King and Jack. He became even more popular by being Sanji's foe in a fight full of character development.
- Surprisingly, Saint Mjosgard of all people became an instant fan favorite upon his return thanks to becoming the first (current) example of a heroic World Noble in the entire story. Him making said re-entrance by beating the absolute shit out of Charloss certainly didn't hurt his popularity any. Sadly, he was executed for this soon afterwards.
- Page One, when introduced early into Act 2 of Wano, was a fairly unremarkable thug who was only notable as he saw the introduction of Sanji's Raid Suit. Come Onigashima, however, and he returned with a new design and a completely reworked personality as the meek Straight Man who was left to deal with his abrasive "sister" Ulti, who had a very attractive design which avoided Oda's common female design traits atop of bearing an amusing resemblance to Nezuko Kamado. Within a few chapters, the two quickly saw an avalanche of fan art and popularity ahead of any of the Animal Kingdom Pirates or Wano characters.
- Yamato, the son of Kaido. He came out of nowhere and blew up hard. He's strong, beautiful, and considered a positive transgender representation.note His popularity propelled them to 11th place in the Worldwide Popularity Poll, before he even appeared in the anime, and became a serious contender alongside fellow darkhorse Carrot to become the 11th member of the Straw Hat Pirates (which, much like fellow speculative Straw Hat Vivi before him, did not end up happening).
- King "The Wildfire" was at first passed over in favor of Queen due to being quieter and reserved in contrast with his fellow Leader Performer's more bombastic demeanor. However, when his mask came off and revealed his true handsome face tons of fans (both male and female) began flocking to him due to how gorgeous he looked. Not to mention the fact his past involved being experimented at Punk Hazard as a young teen for being a Lunarian until Kaido set him free and made him his right-hand man gave him a lot of sympathy from people. His strong bond with Kaido which has been seen as one of the few positive traits of his captain. Finally, Zoro fans love him for finally giving the Pirate Hunter the first truly challenging 1v1 fight he's had since Kaku.
- Although a very minor character, the masked CP0 agent wearing the bowler hatnote became an unexpected fan-favorite during the Onigashima raid for his competence throughout the raid and his surprisingly somber sendoff. After interrupting Luffy's and Kaido's duel and causing Luffy to prematurely lose, the agent says nothing to an enraged Kaido. He simply tips his hat and accepts his fate.
- Despite her limited screen time, Vice-Admiral Doll received a sizeable following due to her unique Goth design.
- Out of the three Seraphim glimpsed in Chapter 1086, Sir Crocodile's Seraphim received the most reactions for his beautiful face.
- Despite being a character created for an anime-exclusive Filler arc, Vice-Admiral Jonathan became well-liked by many fans of the anime for being simultaneously one of the most cunning and one of the most genuinely benevolent members of the Marines, with him posing a serious challenge to the Straw Hats by virtue of his leadership skills rather than pure strength, and acknowledging Luffy as a Worthy Opponent when the Straw Hats prevail, even offering to pardon the Straw Hats aside from Luffy and Zoro for their crimes if they come quietly, even though he didn't think the Straw Hats could escape.
- Isuka from One Piece: Ace's Story gains a fair amount of recognition, despite only appearing in a novel, which are generally considered obscure. This is mainly due to her being Ace's Implied Love Interest, as some official artworks by Oda describe her as, as well as the fact that she's a Fiery Redhead Tsundere like Nami and Koala.
