- 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.
- 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.
- Crazy Awesome 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.
- The only warlord who can rival Crocodile and Mihawk in popularity is Jinbei, the Token Good Teammate of the Warlords who many fans feel is the second coming of Whitebeard in terms of elderly awesomeness. To say that fans were overjoyed when he told Luffy that he would join the crew after finishing off Big Mom was an understatement. Come the Land of Wano Arc, and Jimbei is now officially a Straw Hat, making him a Breakout Character akin to Law.
- Caesar Clown is a shining example of Unpopular Popular Character, as while he rightly despised for his crimes In-Universe but hes just so damn charismatic and pulls the most epic faces that fans (particularly western ones) cant help but adore Caesar. Seriously Caesars chemistry with the Straw Hats was so fun in Zou that a good percentage of fans actually hoped hed 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.
- 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.
- 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. Carrots 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 Luffys crew and become a Straw Hat Pirate herself.
- 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, Sanjis 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 didnt appear in the same arc as Charlotte Katakuri, a character who's the equivalent to a homerun on Odas 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).
- Queen "the Plague" has become a very popular character within the Animal Kingdom 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.
- 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.
Ensemble Darkhorse / One Piece