Among the pups, Dante is arguably the most popular outside of Dylan and Dolly thanks to his cool character design, hammy personality, and the fact that nearly every time he appears, it's a Funny Moment.
The second most popular when it isn't Dante is Deepak, for his WoobieNice Guy personality and his unique spot pattern.
Fergus the fox seems to have a bit of a following as well.
Da Vinci is a pup who only got spotlight in one episode so far. She got a lot of attention from the fans for being unique compared to the other pups. Her spotlight episode, Doggie Da Vinci, is arguably the most popular episode of the series by far.
Summer surprisingly got quite a cult following for a one shot character. She is hands down the most popular love interest of Dylans that the fans like to ship him with.
Deepak has his share of fans as well for a lot of the same reasons as Da Vinci.
Delgado has quite an impressive fan base. It could be largely because hes a Handicapped Badass. He barely did a thing in the series. Rumors also suggest his popularity could come from his voice actor, Jack Binstead, since he was the one who announced the official US launch date of the series.
Two-Tone is without a doubt the most popular Dalmatian in the series, in fact so popular that fans felt she deserved to be the fourth main pup instead of Spot. She's mainly popular for her unique spot pattern and tomboyish personality. She usually appears in the background in most episodes but has had some speaking parts in a few episodes. Her claim to fame was the episode, "Love 'Em and Flea 'Em" where she played a major role and was in a romantic relationship with Lucky. Also, being voiced by Tara Strong just adds to her popularity.
In a similar fashion, Patch has become quite popular despite looking much differently than he does in the movies. Most fans prefer his movie design because it's cuter, but others prefer his series look as it is closer to Dodie Smith's depiction of him.
Tripod has a fairly large fan base, namely for being a Handicapped Badass. A lot of fans like to pair him up with Cadpig (the general reason being that the two would likely bond over their physical shortcomings and insecurities interpreted by the audience), despite the fact that neither of them conversed with each other at any point in the series.
Mooch, the farm bully, both loved and hated by fans alike. Another character that fans like to pair up with Cadpig since they were both in a romantic relationship in the episode, "My Fair Moochie" (even though Cadpig was only pretending to be his girlfriend.)
Wizzer and Dipstick both seem to have a lot of fans. Often depicted as bullies since they're usually seen hanging out with Mooch. They're also well known for having big parts in the live action films and the video games.
As a one shot character, Blaze has also been a subject of Cadpig shipping, except in this case, Cadpig did show some genuine interest to him (such as calling him a "hunk" and batting her eyelids to him). It also helps that Blaze is a Nice Guy with amusing acting talent.
Rebecca was a one shot character for the episode, "De Village Elder", but she became a mega fan favorite for all the same reasons as Two-Tone. Although, the fact that she became a love interest of Lucky's caused a lot of fan pairing wars.
Ivy, Cruella's niece, is the single most popular antagonist, even though she only appeared in three episodes.
Amber, Anita's niece, has gotten quite a cult following for a one shot.
The Dalmatians' hero, Thunderbolt, has an impressive fan base of his own outside of the universe. Some have even gone as far to make fan made girlfriends and wives for him.
Jewel is a Dalmatian pup who did not appear once in the series, but she has appeared a lot in fan art with a particular fan depiction. Fans speculate that if Jewel was a character in the series, she'd have a valley-girl-like personality.
Pretty much every Dalmatian pup with a name who didn't appear in the series has a fan base of some kind (e.g. Penny, Pepper, Freckles, Fidget, etc.), Penny especially, considering she had a fairly big role in the animated movie and was originally intended to be one of the main pups in the series (in some countries, she's in place of Cadpig).
The entireGender Flipped world rivaled the normal one in popularity even before "Fionna and Cake" was made. Special props, however, go to Marshall Lee, who is arguably the most popular one of all, despite his only appearance in that episode being a silent cameo. The episode dedicated to him increased his popularity a billion fold, especially because he's genuinely much more of a mischievous, traditional trickster than Marceline is.
Any character that is female, young, and has a fit humanoid body, including Celina, Doctor Princess, Jungle Princess, the Nymphs, the Bikini Girls and others, generally for fanart, shipping and Rule 34.
Jake's dad, Joshua, seems to be rather popular for how crazy awesome he is.
Before "Jake the Dad" aired, of Jake and Lady Rainicorn's kids, Jake Jr. seemed to be getting the most attention and concern, because the kid lacks a face.
Rosalinen from "Puhoy" is also quite popular, in part to the fact that Finn forgot all about her and their children.
James from "James" seems to have a very loving fan base as well. It helps that, coupled with his funny mannerisms that he's voiced by Brak.
During "Five Short Tables", Ice Queen is revealed to also be writing Gender Flip fan fiction about Fionna and Cake, her fanfic focus on Flynn and Jacques, a gloomy looking boy with bangs covering one eye and wearing formal clothes with his raccoon friend, both got popular instantly. Even Ice President got some fan art and hisGender Flip fanfiction characters, Lynn and Janet also became popular.
Rachel Wilson, Tobias' sister. Despite only having one major role, being written out of the show due to the staff members disliking her, and being a jerkass to the other characters, Rachel remains very popular among the fandom; usually relating to her relationship with Darwin and her aforementioned disappearance.
Clayton, the ball of clay, is loved for his awesome abilities of shape-shifting.
Despite being a blatant Take That! against a Chinese commercial that had ripped off Gumball, Chi Chi's cute design and very meta origins have attracted his own fanbase, oddly enough.
Tina Rex is probably one of the more visually interesting characters on the show (being a realistic CG T-Rex) not to mention having quite some Hidden Depths touched on during the first season, before she was Demoted to Extra from Season 2 onwards. At this point, she hasn't had a single character focus episode since the first season (whereas almost every other character has gotten a few) yet she is still popular with fans. The same applies to her father, and when he showed up in full in "The Routine", many fans loved that.
Gworp from "The Test". He only appears for a few seconds, but his voice, design, and randomness overall caused him to be a popular inside joke in the fandom.
Howdy, Frank, and Grady, the titular antagonists of "The Puppets", due to their creepiness as antagonists, the ambiguity surrounding whether or not they're truly alive, and having had Don't Hug Me I'm Scared alumni on-board in creating them. Given that the characters starred in shorts based upon them soon after their appearance, it's likely that writers knew this would be the case.
Some minor students, such as Josh and Jodie. They are as visually interesting as most characters in the show.
Yuki Yoshida, Masami's mother. Especially because her debut episode features an amazing anime-styled fight with Nicole.
Naturally Pinky and the Brain, the biggest darkhorses in the show, who actually achieved Breakout Character status...
"Gee, Brain! What you wanna do tonight?" "The same thing we do every night, Pinky. Try to Take Over the World!"
Slappy Squirrel has a lot of fans due to being an entertaining Deadpan Snarker and easily outwitting her foes at all times, not to mention her heartwarming and healthy relationship with her nephew Skippy. The news that she wouldn't be included in the 2020 revival was met with mass disappointment by fans.
Rita and Runt's segments get a lot of praise because of Rita's wonderful musical numbers and her and Runt being very dear friends regardless of what they go through.
Wilford Wolf's handsome form is pretty popular, to the point where the majority of fanart shipping him with Minerva depicts him in handsome form.
Minerva Mink, most likely due to the fact that only two cartoons starring her were made and the rest had to be scrapped due to censorship issues.
Also Rita and Runt. Largely due to the fact that their sketch was discontinued after the first season. Rita is popular because many fans find her adorable, plus she has a beautiful singing voice and a cool personality. Then of course, theres Runt for being a dopey comic relief and an homage to Rainman.
Rudolph Mintenberg and Princess War Tickle have a lot of fans as well, although they only appear semi-regularly.
Among the Rogues Gallery, Professor Tite-Gripp and Naughty Kitty are probably the most popular, with the latter often falling under Evil Is Sexy due to being a Cat Girl based on Eartha Kitt and Sofia Vergara.
The redheaded rookie cop seen briefly in "Atomic Hairball" has received her share of fans thanks to her cute design. As did the cat-obsessed brunette with the glasses and the oversized sweater from "AP vs. Disastro".
King Bumi, for being a powerful earthbender, his fun personality, and for being one of the few people who Aang knew before being frozen.
Shyu, the Fire Sage who helps out Team Avatar, proved to be rather well-liked by fans, for being the Token Good Teammate of the Fire Sages, as well as being the grandson of Avatar Roku's firebending instructor.
Jet was originally supposed to be a one-off character in Book 1, but thanks to being a sympathetic Anti-Villain and a Badass Normal, he ended up becoming so popular that the writers brought him back for the latter half Book 2 as a recurring character.
There's also June, a Badass NormalBounty Hunter, who, in spite of only appearing in one episode, became rather popular with fans, which the creators even commented on. This is likely why she reappears in the Grand Finale.
Although it's not exactly as much "popular" as "well-remembered", Koh, the Face Stealer. He barely had any plot-importance even the two times you see him (one was a flashback), but he's just so damn creepy that he's become a frequenter of fanworks and Epileptic Trees all the way up to the end of the show.
Ty Lee isn't really as important or developed as her friends Azula and Mai, but she's loved by the fans for her unique ability, Foe Yay with Sokka, Genki Girl personality, and cute design.
Huu, the old man living in the swamp, is rather well-liked by fans for his Cool Old Guy personality, his awesome swamp monster disguise, and his role during the invasion on the Fire Nation.
The Big Bad Hippo, one of the contestants in the Earthbending tournament Toph participates in, became popular with fans for being a Mighty Glacier with Hulk Speak. It's likely for this reason that he ends up returning alongside the Boulder to help out during the invasion on the Fire Nation.
Jin only appeared in one episode in Book 2, where she went on a date with Zuko. In spite of this, thanks to her cute design, Nice Girl personality, and status as someone to ship Zuko with, she ended up becoming rather popular.
General Iroh is only given a major role in the Book 1 finale, but proved to be popular with fans for being Zuko's grandson, a Four-Star Badass, being named after Iroh, and being voiced by Dante Basco.
Zhu-Li barely says a word throughout the entirety of Book 2, yet still became very well-liked by the fans for being The Comically Serious and the assistant to the equally popular Varrick. It's probably for this reason that she saw an expanded role in Book 4.
The frog-squirrel that appears in "The Coronation" is well-liked by fans for its strange yet cute design.
Fire Lord Izumi gets a total of one scene in the entire series, yet is still very popular with fans for being Zuko's daughter, as well as a Reasonable Authority Figure who's clearly learned from the mistakes of past Fire Lords.
On the villainous side, Grim Reaper won over a lot of the fanbase with his debut appearance- a big Moment of Awesome breakout. While callous, he's also an Adaptational Badass and Creepy Awesome, unlike his comic book counterpart (who was pretty lame).
Ultron is very easily one of the most loved villains in the show, despite only acting as an antagonist in four episodes. An unofficial poll deemed him the most popular villain by a longshot.
Mockingbird has become regarded by fans as a fun character, despite only making three appearances under that alias. There's a significantly vocal group who wished she became part of the New Avengers. The choice to give her a bigger role in the Secret Invasion arc was actually thanks to Chris Yost noticing the positive reception she got.
Doctor Doom won fans over even before his first episode premiered. His actual feats didn't disappoint either; he overcame six Avengers and the entire Fantastic Four in a battle, and found a Skrull among them even before they could. Doom did another guest spot 10 episodes later, in which he helped Iron Man create a weapon to expose disguised Skrulls. Doom explained that he spent so much time trying to prevent the Skrulls from taking over the world so that eventually, he could take it over instead.
As Iron Fist and Luke Cage beat up thugs, cracked dry wit, and helped track down the thief of Hank Pym's Ant-Man suit, the viewers wished they could watch these Heroes For Hire kick even more ass in their own show.
Ben 10: Ben is technically an army of Ensemble Darkhorses, being a shapeshifter who can assume various alien forms, across the series he gets a lot of forms that are heavily popular amongst the fans even when not playing an especially major point in the plot or even having limited appearance:
Articguana and Buzzshock, two of Ben 10,000's aliens, became rather popular, with fans wanting to see them be unlocked. The fans got their wish with Articguana, who finally got used in Omniverse, and Buzzshock a couple of seasons later.
Regular-Sized Rudy has found many fans for his positive attitude and thrill-seeking tendencies in spite of his asthma.
Millie Frock from "Fort Night" gained fans from being so hilarious and disturbing, and they've repeatedly brought her back for more episodes. Thankfully her appearances have been far enough apart she hasn't lost her entertainment value.
Marshmallow, for being one of the few positive portrayals of a transgender person in fiction when introduced in Season 1's "Sheesh! Cab, Bob?" from 2011.
Nat Kinkle, the limo driver from "V For Valentine-Detta". Fans ate her up after 1 appearance, leading to a return in 2 episodes during season 10. Even getting her own focus episode in her 3rd appearance.
Kelsey Jannings, the snarky director who works with BoJack in season 2. While she's abrasive and not the most pleasant person to be around, she's fair to those that earn her trust and is one of the few Hollywoo higherups that isn't Only in It for the Money. Fans took a liking to her and were sad to see her subplot abruptly cut off after she was fired.
In season 4, Yolanda gets this spot, due to her becoming Todd's first asexual Love Interest, with the season ending with the implication that they are going to start dating soon.
Even if she isn't a real character, a lot of fans seem to like Ruthie for her general perky attitude and cuteness.
Flip McVicker got a lot of notice as a spot-on parody of pretentious writers pointlessly obsessed with being "clever" and using True Art Is Incomprehensible as a defense for every problem people bring up with their work. It also helps that he's actually voiced by the star of a show that's been accused of epitomizing this mindset.
Bonkers: Wacky Weasel, a one-shot villain actually has a good amount of fanart and screenshots on the Internet.
Rollo Goodlove, for always proving himself to be a delightful Magnificent Bastard in his three appearances.
Bubble Guppies gives us Nonny, the orange haired guppy that, as of the second season, gets less screen time than the others and is notorious for never smiling.
Captain N: The Game Master: Mike, a former friend-turned-bully of Kevin's, only shows up for one of the earlier episodes (sort of; it's really a robot modeled after him), and yet he seems to be well remembered by the fans.
Care Bears: Baby Hugs and Baby Tugs started out as dark horses during the early days of the franchise. However, a majority of the Nelvana TV series is focused on them.
Castlevania (2017): Blue Fangs gained a fanbase even from those who weren't Rooting for the Empire (despite only appearing in one episode, of course) the moment he laid a verbal smackdown on, and afterwards killed, the bastard bishop who cemented himself as a very forgettable Hate Sink due to having arranged for Lisa's death and kickstarted Dracula's plans for genocide. Fans even fell in love with one of his famous quotes, "Lies? In your house of God? No wonder He has abandoned you."
Foxglove, the witch familiar bat from "Good Times, Bat Times" lovestruck with Dale. She only appears in that one episode. But she gets loads of fan art, she seems to appear in more Fan Fiction as the literal Sixth Ranger or at least as Dale's girlfriend than not (mind you she and Dale were shown as a couple at the end of the episode, and a show that airs its pilot as episodes 41 through 45 is nowhere near any chronological order, so this might actually have been the chronologically last episode), and she even has a website dedicated to her with masses of contributions from the olden days of the fandom. She even managed to convert lots of even earlier Rangerphiles from then-dominant Dale+Gadget to Chip+Gadget because she and Dale make such a cute couple. Her immense popularity brought her back as a regular character and the Sixth Ranger in the Boom! comics.
Tammy's mom, who is never even named, has gained a fan following as well.
Lahwhinie/Lawhinie/Louwhiney. She only appears in "Gadget Goes Hawaiian", but she's essentially Gadget's Doppelgänger, a kind of Gadget in a sarong wearing make-up and a flower in her hair. Yes, she's a villain. No, she is not redeemed in that single episode of hers. But she technically is even more of a looker than Gadget with lots of Fan Art to prove, and she's pure Canon Fodder for the Rangerdom's ever-productive Fan Fic writers: How come there's a mouse in Hawaii that looks almost exactly like Gadget? Even if they don't try to answer the question whether she's Gadget's Long Lost Sibling or even Evil Twin, they can still bring her back as a Gadget impostor.
Geegaw Hackwrench. Gadget's Disappeared Dad isn't even a character. He only ever appears in one of the five parts of the pilot, and that's in a framed picture for some two or three seconds. That, and he might not even be alive anymore. "Might" because Disney applied the Never Say "Die" rule in a way that leaves his real fate unclear. What few things we learn about him from Gadget and his old buddy Monterey Jack make him some serious Canon Fodder. He is featured in Flashbacks in the Boom! comics, too.
Clarence has many popular minor characters from Kimby, Chelsea, Dustin, Nathan, and Breehn, but none can top Amy Gillis who had only one episode appearance and two brief cameos.
Van Gogh. After the first episode he only ever appeared in cameos, but it's not hard to find fanart of him.
Ponce is a very popular character. Despite being created to mock the Tonight, Someone Dies Trope, his friendly nature, the genuine sadness JFK feels upon his death, and the fact that the best Heartwarming and Tear Jerker moments came from his death makes him a surprisingly popular character.
Despite his scant role in Code Lyoko, Clone William's calm idiocy and "adorable" personality made him a hit with fans- even moreso than William himself.
Sector Z! After five minutes of screentime in the movie they won the hearts of a sizeable portion of the fanbase with their badassery. It probably helps that they were the Delightful Children from Down the Lane before they were Brainwashed and Crazy.
Rachel, a.k.a. Numbuh 362, who literally ate her way through broccoli to stop the spread of it. Not to mention, a lot of fans pair her with Numbuh 1, causing her popularity to raise even higher. On the Kids Next Door Wiki, they had a poll where users could vote on their favorite operative. Numbuh 362 had more votes then Numbuh 2, a main member of the team.
Tommy Gilligan, a.k.a. The Tommy, Numbuh Two's younger brother. He was a big secondary character later in the series, but only because of his popularity early on.
Fred the Barber Half the show's references on this site are about him. He was the least dangerous but most memorable villain.
Di Lung. To the point where he would appear more frequently during the later seasons.
Katz is another example. His popularity may be the reason he appears more often than other villain on the show.
King Ramses' is quite popular despite the fact that many find his episode to be the scariest. In fact, the reason as to why most people assume he is scary is possibly an excuse to make him seem more popular.
Freakshow, the only human character who could truly be considered an antagonist. He only appeared as the Big Bad of one episode, and the third TV movie, but is one of the more popular villains, with the general consensus being that They Wasted a Perfectly Good Character.
Stacy Rowe is possibly the best example, as her popularity with the fandom was likely the reason why she got an actual, honest-to-goodness recurring subplot in season five, which, for any Lawndale High character not named Daria, Jane, or Quinn, was really quite a feat.
Daria's Cool Aunt Amy, despite only showing up in three episodes (one of which was a cameo).
Lisa the babysitter. She only appears in a very early episode of the series and never shows up again after that. But look up any fanart of her and you'd be surprised at how much of it there is. Guesswhy.
For similar reason The Touchy-Feely Neighbor Lady and Candi, the Dee Dee replacement, are widely remembered despite only appearing in one episode.
Mandark's abrasive younger sister and Dee Dee's rival-turned-friend Lalavava only appeared in one episode, yet has a substantial amount of fanart, enough to have gained her own category in some fandom groups for the show.
Lee-Lee, one of Dee-Dee's friends, is one of these
Douglas Mordecai, one of Dexter's friends, despite being a borderline Satellite Character in canon. Maybe just because he was the only character Dexter could talk to like a human being.
Val Halen has a ton of fangirls.
The Puppet Pals. Some people wished they had their own Spin-Off.
The robot parrot from the episode "The Parrot Trap", thanks to being a Fountain of Memes with lines such as "Dexter is a cookie!".
Doug: Roger Klotz and his gang, the chief antagonists. Also, Doug's older sister Judy Funnie.
The Dreamstone: Mech Beav only appeared in one episode, but is popular with many fans due to being a cute machine, having an adorable loyalty to Blob, and being the nearest the Urpneys had to a Mascot Mook.
Glittering Goldie, who appeared in only one Carl Barks story, appeared in several episodes. The relatively few occasions she appeared showed her as plucky (she even has a pet bear!) and cunning. Pairing her with Scrooge (Scroldie) is still one of the most popular ships in the fandom.
Gizmoduck, plain and simple. He turned an accountant into the most powerful array of mechanical components and accessories who is a bodyguard and security guard for Scrooge, as well as a super hero to Duckburg and even went on to help Darkwing Duck protect St. Canard.
Rolf is probably the most popular of the kids, for being funny, quotable, and Crazy Awesome. Even the show's creator Danny Antonucci said that Rolf was his favorite character and many fans agree with him.
Marie, the blue-haired Kanker. She has a much larger fanbase than any other girl in the show and is often considered to be the most attractive one, despite not being intentionally designed as such. Pairing her with the object of her affections/psychosis, Edd, is probably the most popular 'ship in the fandom.
Her sisters get this to a lesser degree, but more so to May, who is fairly well-liked for being the most individual of the Kankers, and from the fact that she seems to genuinely love Ed, as evidenced in the Valentine's Day special.
Nazz, the Girl Next Door of the Cul-de-Sac. Especially in her later appearances, she's mostly just a supporting character in the show who often tags along with the Kids. Despite this, fans have a huge following for her because of her sunny nature and for being the kindest of all the girls in the show. Additionally, Ship Tease has also elevated her popularity within the fandom, where she's been frequently paired up with the other characters, most especially Kevin and Double D.
Plank. Fans who have made stories focusing on that piece of wood make him out to be secretly an evil genius due to apparently being sentient and being only able to "talk" to Jonny. Also, there's a plushie of him◊.
Ms. Doombringer, a highly competent fairy hunter that appeared in just one episode but has people asking for more.
Molly, a girl that showed up for one episode but already has shippers pairing her and Timmy together.
Remy Buxaplenty to some degree - he appeared in one episode to challenge and lose to Timmy in a duel, and disappeared after that. All the same he had a fairly significant following and a tendency to be shipped with Trixie Tang - who wasn't even in the episode he was in - and years later was brought back for a small handful of new episodes.
Dark Laser. Initially, he was a one off villain. Then he made an appearance in the fifth season as a continuity nod, but by the sixth season, he'd become a semi-regular, even having a major part in the season finale.
Anti-Cosmo is quite popular among the fandom, especially the idea of Timmy being his godchild. No wonder Foop is The Scrappy.
Gary, Timmy's imaginary friend, who only ever appeared in two episodes (one of which was just a continuity nod) but is also very popular with the fandom.
Princess Mandie, who's one of the few competent villains in the series and looks like she came out of Danny Phantom instead. She only appeared in three episodes (plus a cameo in a fourth).
Veronica. She has little to no significance within the show other than being Trixie's inferior best friend. In spite of this, she seems to have a fairly large fandom appeal even when she's underused with the show, with some even thinking that she's better than Trixie herself. She's even shipped with Chester, another fellow blonde character of inferior status (to AJ).
Numerous characters in Family Guy. Includes Ernie the Giant Chicken, Death, the Evil Monkey, Ollie Williams, Seamus, Herbert, Greased-up Deaf Guy, and Bruce (the Performance Artist that has "Oh no!" as a Catch Phrase) are all popular among fans. They were also one time characters before cancellation but due to their popularity they became Recurring Extras soon after.
Scruffy was a popular character during the interim when Futurama was not producing new episodes. He only made a few appearances in the original run, and was mostly noteworthy for his extreme apathy. Since the revival, Scruffy has had a much larger role, frequently appearing alongside the main cast, almost solely due to his popularity on the Internet.
Wade Duck from the U.S. Acres side is one of these. His cowardice was so over the top, you couldn't help but laugh (believing he would go to prison for removing a mattress tag, that staplers spy on important documents and will take over the world, that football players in a huddle during a game, no less are talking about him behind his back, etc.) Bo was one as well, to a lesser extent given his laid-back attitude and despite the fact that he was not seen nearly as often as his twin sister, Lanolin.
Despite only appearing in three U.S. Acres, Aloysius Pig from the same segments has a pretty small following for complaining about activities people wouldn't find troublesome and being voiced by a popular comedian, Kevin Meaney.
Generator Rex has Breach, who gained a bunch of fans due to a combination of some Foe Yay with the main character, and being attractive while being delightfully creepy at the same time. It got to the point where the fandom had a collective freakout when she seemed to be killed off, then rejoiced when it turned out she was fine.
Max's cousin Debbie only appears in one episode ("Leader of the Pack"), but is almost as popular as the main cast.
Mrs. Pennypacker also only appears in one episode ("Date with Destiny") and is also very popular, though not quite as popular as Debbie.
One of the Trekkies in A Goofy Movie has reached meme status despite having no name, no plot relevance, and only two lines (spoken by different actors) in the entire movie.
Bigfoot. Plenty of people testify that his short suite of scenes were the funniest part of the movie.
Beret Girl in An Extremely Goofy Movie is extremely popular, despite having no name and only appearing in four scenes, because of her appearance, her interesting personality, and the fact that she's the final love interest for PJ.
Ain't nobody tell Dracula what he gonna do! Dracula was born knowin' what he was gonna do!
The number of episodes Sir Raven appears in can be counted on one hand, but that doesn't stop him from being one of the most popular characters to come out of the show.
Grojband: The title band's semi-regularly recurring rivals, The Newmans, are pretty popular with fans despite being just Rule 63 versions of Grojband (although that is probably a major reason for their popularity). Laney's counterpart Larry (later retconned as Lenny by the creators) is especially loved by fans for being shy, nervous, and dainty (in contrast to Laney) with a huge unrequited crush on his band's leader.
Spokesperson!Atticus and Actress!One-One. They are only there for a quick joke in Episode 5, but are very memorable for the sheer absurdity of it.
On a similar note, Mirror!Atticus and Mirror!One-One are a (One-)One-Scene Wonder, due to establishing that Car inhabitant reflections have opposite personalities, which is technically Fanfic Fuel.
"Good Guy" and "Bad Guy" from Tulip's game are really just background decoration, but they stuck with fans, to the point that they are official icons on the show's subreddit.
Randall has gotten a lot of recognition for being a friendly, sentient water puddle who is completely willing to help Tulip catch up with the Cat. Some would've liked to see him as the fourth party member, but that would've been too many characters to juggle. He becomes a recurring character appearing in one of the Train Shorts and an episode in Book 2 and 3.
Nancy only appeared in one episode, and only at the very beginning at that, but fans remember her for her friendly personality and Creepy Cute design. She returns for a small cameo in "The Lucky Cat Car".
Alrick is only really important for the Conductor's backstory, but many fans understand why she was in love with him so much, since he was an Adorkable goofball who reliably stayed by her side throughout their entire lives.
Frank the Bear only appears briefly in Book 3, but many fans love him for being a Moment Killer and a genuine Nice Guy.
The Chandelier Escort from "The Debutante Ball Car" gets a lot of love for his design and voice, despite only appearing briefly.
If you judged this show by the fan works, you'd assume that Tak was a major character; in fact, she only appeared in one double-length episodenote not counting vocal cameos by her ship's computer in two others. She had one planned reappearance before the show was Cut Short, but it's certain her popularity would have resulted in many more. Given that she was the first competent Irken we had ever seen, and made a great Foil for Zim, and as a new female character she offers several shipping possibilities.
THE MOOSE! Seriously. The Moose has its own fanbase just for being so damn impressive.
Minimoose, who only appeared in one episode before the show got cancelled, makes regular appearances in fanart and fanfic, usually as the Woodstock to GIR's Snoopy. He's just so darn cute...
Jade's (technical) Superpowered Evil Side, the Queen of the Shadowkhan. Despite only showing up in one episode in Season 2 (and getting a brief mention by Tarakudo in Season 4), there are quite a variety of stories in which she regains the powers and/or personality of the Queen. (See Project Dark Jade.)
The Demon Sorcerers also count, though not to the same extent as Queen Jade because they got more screentime. They were a Big Bad Ensemble in the second season, but were never heard from again after their defeat. The fandom loves these guys, who were each given decent and distinct personalities despite only really getting one episode each, plus a few group appearances.
In particular Hsi Wu, the sky demon. Somehow the one episode he has a significant role in managed to make him a fan favorite for shipping with Jade. Or else everyone just hates Paco that much...
From Jem we have Stormer in the Misfits. Her popularity is fueled by her being the Token Good Teammate of the Misfits, albeit she is capable of having a nasty attitude from time to time. She's the overall creative force behind her band but she never gets credit for it, and usually winds up helping (secretly) the Holograms when she absolutely feels she needs to. Stormer has also been the only Misfit to be offered a place in the Holograms, but she turned it down because she felt the Misfits needed her more. Word of God has it Stormer's first loyalty is always going to be the Misfits regardless, which really only makes her more likeable; she sticks by her friends.
Saffi doesn't appear very frequently, but she's easily one of the show's most popular and well-known characters because of her Cute Monster Girl design, Cloud Cuckoolander personality, and well-received relationship with Beezy.
Peep doesn't appear super frequently but he's pretty well-liked in the fandom, because his crush on Heloise, his memorable Cockney accent, and his pickpocket/con artist characterization make him one of the primary reasons for many to watch Season 2 episodes.
Despite never appearing on-screen and being mentioned only once in the series, Lucius I is quite popular with fans, due to his reputation as The Dreaded and his intimidating appearance being a vast source of Fanfic Fuel.
As she was in her previous appearance in the DCAU (which was back in Batman: TAS), Zatanna is very popular with fans due to her attractive design, voice, cool magical abilities, kind personality, and friendly relationship with Batman.
Giganta. Fans find this version of character attractive and adorable. She has also Ship Tease with the fan-favorite Flash in the last episode.
Vigilante. Being a superhero cowboy voiced by Nathan Fillion will do that for ya.
Anemia and Iodine from their self-titled short. While only having one short, they managed to gain a bit of a following (the former especially for being a Perky Goth cat girl) and are the only characters from a one-shot short to have gained any fanart online. The fact that the director of the short worked on Rocko's Modern Life and thus the characters had a similar visual style to the show didn't hurt.
Among Life With Loopy fans, there's Larry's girlfriend, Stacey. She made her only appearance at the end of "Larry's Girl", late into the series' run, and had only one line of dialogue. Due to her scene being one of the sweetest ones in the show and overall being a very cute character, she became very popular with fans of the short and has received a bit of fanart.
Many Loopy fans also really love Raquel and Saffron from "Bull In A China Shop" and "Larry's Girl" respectively, despite them only appearing once.
Eugly the rabbit, who doesn't say or do much in the event that she even appears in the episode. However, a lot of fans like her because she's genuinely kind (most of the characters on this show are jerkasses), and there's a quite a bit of fanart dedicated to her.
Ursula, Stumpy's girlfriend. She's mentioned in passing in some episodes and has made a total of two physical appearances on the show, yet she is featured prominently in fanfics.
Electronique was rather popular with fans, more than you'd expect from her single appearance. But then again, she was a Baroness and Gadgeteer Genius with electrical powers, a short temper and a hammy accent from somevhere in zer centre of Europe, so she was a memorably entertaining character, and as a villain in Shego's hometown she had a connection to the fandom's favourite villian.
Jasiri from The Lion Guard is this for being a good hyena, and having (arguably) the best song in the show.
Cheetata and Cheetato from Timon & Pumbaa. These two sophisticated cheetahs seem to be gaining a fanbase.
The Mask: Any Mask personas that appear in one episode other than The Mask
Eve is a female version of The Mask and like him she is genuinely insane but good hearted like him as she saves Stanley from Pretorius which makes her popular with the fans and her sweet nature towards him as well makes her even more popular.
Masked Dr Neuman is terrifying and scary as he shows what could happen if The Mask decided to become a supervillain instead of a hero but he is popular because of these things and the fact that like The Mask he has his funny moments and being Affably Evil as well which makes him more popular as well.
Masked Peggy Brandt is egotistical, vapid and vain but however these things along with the fact that she is very hilarious while being any of those things makes her very popular while still having a good heart like The Mask makes her this even more.
Littlest Pet Shop (2012) gives us Sugar Sprinkles, the stoner-esque cat who lives in the Sweet Delights truck. After appearing in a single episode in season one and getting as much fan attention as the main pets, she came back for a single episode of season two, as well as another episode appearance in Season 3.
One of the strangest examples: the nameless drunk cat with the red nose, big lips, saggy jowls, dickie shirt with bow tie and bandage on his tail. He only appeared in the Bob Clampett-directed "Kitty Kornered" as a pet of Porky Pig who teamed up with Sylvester and two smaller cats, but he proved popular enough to appear in many of the spin off series of the 1980's and 90's including Tiny Toon Adventures and The Sylvester and Tweety Mysteries.
To a far lesser extent, Penelope Pussycat, originally the unlucky nameless cat who would get chased by Pepé Le Pew in his shorts has been gaining her fair share of popularity these days as well.
There's also Michigan J. Frog. He appeared in just one seven-minute short, but is one of the more popular and recognizable minor characters in the Looney Tunes universe.
Cristina, Lincoln's crush from "Making the Case", gained popularity in the fandom despite not even having a single line in her three appearances, often portraying her as a rival to Ronnie Anne or the series' equivalent of Lila Sawyer.
Clyde's parents are popular due to their status as a gay couple. It helps that the show does not attempt to draw attention to this fact, instead focusing on how they are Good Parents to Clyde.
Carol Pingrey, the girl whom Lincoln uses to coerce Lori into being a part of his revised family portrait by threatening to replace her with Carol, due to her looking similar in "Picture Perfect". She appears onscreen during a few seconds, gets a few blink-and-you'll-miss-it mentions afterwards, and doesn't have any line; but she is popular in the fandom. She generally acts as either a rival to Lori (with differences whether she's a sympathetic one or not), Lori's Sitcom Arch-Nemesis whose only joy in life is messing with Lori, a friend of Lincoln (or more than that), a friend of Leni, or even a mix of those portrayals. She was eventually given focus in "Selfie Improvement", in which she's revealed to be Lori's Sitcom Archnemesis since kindergarten, albeit a sympathetic one. They eventually form a friendship at the end.
Kirby from "Out on a Limo", enough for fans to hope he returns in a future episode.
Lincoln's dates in "Dance, Dance Resolution" are popular for the following reasons:
Tabby, the punk girl, became popular long before the episode even aired, as a brief scene with her appeared on a Nickelodeon music video about a month before the episode premiered.
Haiku, the goth girl, gained some recognition, especially once she starts bonding with Clyde.
Giggles for being a legitimately nice girl and, unlike Luan, only teasing Lincoln harmlessly instead of mocking or hurting him with pranks.
Polly Pain for both her design and interesting interactions with Lincoln.
The gender-bender versions of the Loud sisters from "One of the Boys" (and Linka, the gender-bender version of Lincoln) have become very popular even before the episode aired, especially Lars (the male version of Lucy), Loni (the male version of Leni), and Loki (the male version of Lori).
Maggie, the 13-year-old emo girl from "Funny Business", is pretty popular among fans (especially on Tumblr and DeviantArt). So much so that it's common to find her getting shipped with either Luan or Lincoln.
Nikki, Ronnie Anne's tall friend from "City Slickers" became incredibly popular with the fandom.
Leni's second prototype design (the one in the top right) is considerably popular, probably due to looking like a mix between both her final design and Lori. Interestingly, several of her design elements ended up being used for Carol Pingrey, listed below.
Lincoln's lookalike in "Cereal Offender", who is officially known as the Bratty Kid, has some popularity in the fandom. He's speculated to be related to Carol Pingrey, even to the point of being her younger brother to further parallel with Lincoln. Proposed names for him include Linclone and Wilkes.
Pop-pop is also fairly popular as the resident fun grandpa.
In Metalocalypse, a show about the five members of a death metal band, who emerged as the most popular character? Their manager, Charles Foster Ofdensen. Fending off an assassin and making said assassin stab himself helped.
Red Action was quickly embraced by fans, thanks to her rather Animesque design, cool factor, and interactions with Enid. Red's following substantially increased after "Back in Red Action" aired, revealing her backstory as a Sentai-inspired runaway from the future with a heavy dose of romantic overtones with Enid.
Thanks to Drupe's thick hips and thighs, there's been a lot of fan art of this strawberry girl.
Succulentus only appears for a few minutes, but fans were drawn in by his numerous nu-metal references. Helps that he's voiced by Korn lead singer Johnathan Davis.
When Cosma made her debut, people immediately fell in love with her thanks to her design and her Pragmatic Villainy attitude when she points out the problem of Boxman constantly attacking the plaza. Not to mention she's voiced by Marina Sirtis, who played Deanna Troi in Star Trek: The Next Generation.
When Enid's Parents were introduced, fans immediately fell in love with them, due to being a incredibly sweet, polite, and cool vampire/werewolf couple. The fact that they're both pretty attractive has also won them some points.
Everest, spawn off a huge fan base before her debut episode even aired! She only appears in some but not all episodes, which places her in Ensemble Dark Horse territory.
Chickaletta surprisingly has a big fan base too.
Tracker was announced over a year before his debut, but at first, the fans didn't talk about him very much. After his debut in "Tracker Joins the Pups", however, he became very popular and was gladly welcomed into the fandom.
The Mer-Pups, who have so far only appeared in two episodes, have also gained a fairly impressive fan base.
Sweetie quickly became a fan favorite and now currently stands as the show's most popular antagonist.
Another antagonist pup, Arrby, has become quite popular with the fans as well. Even though he is a sidekick to the antagonist, Sid the Pirate, he still acts like a nice guy, which helped make him a very adorable character from the fans perspective.
With the fanbase the size as it is, a case can be made for most (if not all) secondary characters, with the Fireside Girls (Gretchen in particular, since some fans pair her with Ferb) being the most prominent examples.
Eliza Beckham Fletcher, it is unlikely she will show up again yet she already got a sizable fanbase following less than 2 days after the one episode in which she does aired.
As for background characters, the female backup dancer with the brown hair in the "S.I.M.P." song and "A Real Boy" has gotten a lot of attention. To the point where she got a speaking role and a Fanservice Pack in the Halloween special "Night of the Living Pharmacists". Apparently her name is Dana.
Planty the Potted Plant has accumulated a large fanbase too, including members of the staff who tried getting him more screentime. Unfortunately his scenes were mostly cut.
While most of the pups in the show were intended to be one-shot characters, some have gained some big fan bases. For instance, the puppy known as Pepper became a mega fan favorite (most likely because of her tough girl personality) so much that she was brought back in a Season 3 episode working with the Super Secret Pup Club.
Lucky's father, Slik, has an impressive fan base, mainly due to his striking resemblance to Tramp from Lady and the Tramp.
Cupcake started out as a dark horse. Everyone (both the fans and the show's creators) found her to be so cute that she quickly became a permanent recurring character starting in Season 2, except with a more down-to-earth personality rather than an innocent cute kid.
Lucky's owner, Dot, introduced in the Season 1 finale, has become likable enough that she would recur more often in Season 3.
The Rowdyruff Boys. Who were evilmale counterparts to the titular three main characters who only appeared in one episode due to being killed off. Mere days after the episode first aired, the Internet was swamped with dozens of fanfics and fanart pieces devoted to them. Entire websites - exhaustive websites, full of art, episode transcripts and bustling forums - were created in their honor. The fans were almost unanimous in the desire to see the boys come back. After four years of demand, they finally returned in season five.
Bunny only appeared in one episode, yet is a popular character.
DupliKate won over some fans with both a cute design and likeable personality that is the perfect kinda Ham and Cheese for the show. The fact she actually does give the girls a challenge helped.
A few fans found the butter boy aka "Butterfingers" pretty interesting. A villain who motivation was wanting to be a superhero but resorted to un-supehero like methods (i.e stealing Buttercup's body) because the power he gained wasn't to his liking. The fact that he has a very skewed perception of superhero-ing (solely just fighting bad guys for action rather than protecting people) and willing to kill to keep Buttercup's body was a factor too.
Cornchip Girl, Butch, and Lawson also have sizeable fanbases.
Miss Grotke, for being a MoeHippie Teacher with hints of Sensei-chan here and there (and was pretty popular among the show's older male fanbase)
The "Bad Kids" consisting of Conrad Mundy, Greg Skeens, Sue Bob Murphy, Kurst the Worst, and Lazy Kid are quite popular despite only having large roles in a few episodes. It isn't too hard to find fanfics with these guys in it.
Robotgirl is easily one of the most popular characters in the show, despite only appearing in two episodes. Youd think she would have a bigger role judging by all the fan art she gets.
Protoboy, who appeared in four episodes is nearly just as popular as her. Being almost unanimously the most beloved villain due to being Robotboy's older brother, being moreserious then most of the other villains and being considered cool. He was originally a one-shot villain, but his return later on may have been in-part of his popularity.
Morose. One episode was all it took for her to become popular. Perhaps her voice might have helped?
Heck, Misery's cousins in general are quite popular, but special mention, aside from Morose, goes out to Malady and Malaise - their popularity was probably helped by not only having had appeared in an earlier "Misery family" episode, but also for actually being rather kind to others compared to, say, Mildew or Migraine. Makes Misery's description of them being "cold" all the more ironic, huh?
The Scotsman. A big, loud, barrel-chested walking stereotype with a huge Scottish claymore and a machine-gun for a leg who picks a fight with Jack for no real reason at all. Usually when a baddie does this he's curb-stomped by Jack in one blow, but fans were shocked and delighted when The Scotsman instead evenly matches Jack, fights him for a straight day, and the battle ends in a tie when they are both too exhausted to continue. The guy went on to return in a later episode, then gets A Day In The Lime Light episode where he saves Jack's life repeatedly over the course of a two-part episode. The Scotsman's daughters, who were introduced in Season 5 also deserve special mention for being an Amazon Brigade of young and hotbut heroically built ladies.
Demongo got a pretty big fan base as well (despite only appearing in one episode), enough to even get him a profile on Cartoon Network's site at one point in their old shows archive. He also makes an appearance on the game FusionFall.
The Guardian of the time portal is well-loved by fans for being the only character to unambigously and truly defeat The Hero Samurai Jack and fans are hoping that he reappears in Season 5 with a rematch with the more experienced samurai. Unfortunately he did, and when we mean unfortunately, we mean being Killed Offscreen by Aku without much fanfare, to the dismay of many fans who were hoping that another rematch would have happened.
Exdor, who seemed very similar to Dexter. He later appeared in the 2004 video game.
X9. His episode was an excellent noir episode, and he had an excellent 1920's mobster theme. Shame he was forced to go against Jack... which only meant one thing.
Ikra, Aku's female alter ego, is popular enough to be shipped with Jack.
Da Samurai has also been picking up some steam as well. People seemed to enjoy his change towards the end of his episode, and some even hope he comes back for season 5. They got their wish as he makes a cameo in the sixth episode.
Despite appearing only in the opening scene of Season 5, the unnamed family of humanoid dog aliens referred to as the Emoji Family is quite adored by the fanbase for being cute and adorable due to using emoticons to communicate with each other, and they spawn a lot of fan art.
Scaramouch partly for being the comic relief to break up the heavy drama and tension for the rest of the episode, and for how his fight with Jack is the perfect blend of intense, creative and ridiculous. His popularity would skyrocket the moment he uttered one dirty word that caught every viewer by surprise because it would never get away with it in previous seasons and it turned into an instant Memetic Mutation.
The bounty hunters from "Sonic Search and Smash Squad", largely due to their reappearance in Dr. Robotnik's Mean Bean Machine, a rather extreme example of this since outside the game, most of the characters only appear for all of a couple of seconds in the show itself.
Sonic the Hedgehog (SatAM): Bunnie Rabbot arguably had the least spotlight of the main Freedom Fighters, acting as a bit player at best in every appearance, is popular for her cyborg powers and is one of the few alternate media Sonic characters not to gain much disdain.
Mary's mom: I remember when they first invented chocolate. Sweet, sweet chocolate. I ALWAYS HATED IT!
Star vs. the Forces of Evil: Mariposa Diaz became popular even before she was born (back when she was known as Marco Jr.). Plenty of fans took an interest in her potential as a best friend and Foil to the reborn Meteora Butterfly, which was only fueled further when the episode "Gone Baby Gone" showed the two as teenagers with a close bond.
Shaak Ti became a fan-favorite after her arc of protecting the Chancellor. Not only did she have the unenviable task of going up against General Grievous and his Magna Guards back when they were considered The Dreaded, (Grievous alone defeated a group of six Jedi fighting him at once earlier,) but she managed to really hold her own against their onslaught due to clever tactics, and as a result ended up being the only Jedi who survived the ordeal. The cool fighting, her caring personality, the selfless sacrifice she made to save the group (even if it ultimately didnt work), and her cute design all endeared her to fans. So much so that it seems she inspired the choice to create another Togruta Jedi, Ahsoka Tano, to be the apprentice of Anakin Skywalker himself and a main character in the 2008 series. (Shaak Ti could not fill that role herself due to her background appearances in the first two prequel movies establishing her as a Jedi long before Anakin ever became a Jedi Knight himself.)
Durge was ultimately a Starter Villain in the series who got taken down by Obi-Wan very early on. However, as a Bounty Hunter with cool regenerative abilities and a menacing presence, he became so popular to fans that Disney has ultimately made the decision to bring him back into the Star Wars canon long after the series itself was removed from it.
Asajj Ventress was ultimately a Disc-One Final Boss who was meant to die after her fight with Anakin to push him further toward The Dark Side. However, due to being a creepy yet cool Dark Action Girl who dual-wielded with style, she became popular enough to get saved in other expanded universe works, and even became a prominent character in the 2008 series with many more storylines of her own.
At the time, General Grievous achieved this status for being a nearly-unstoppable Hero Killer who was at the center of what many fans considered to be the best fight scenes. Notably, out of the nine Jedi he was seen fighting, only four of them survived, two of those survivors were hospitalized, and only one of them actually defeated him (Mace Windu, who happens to also be the only Jedi who possibly defeated Darth Sidious himself.) Unfortunately, severe Villain Decay hit him after this and he is now loved more ironically than genuinely, but this incarnation of the character has remained beloved nonetheless.
Very minor Jedi Shaa Gi is remarkably popular due to being an Expy of Shaggy Rogers, who has quite the fanbase himself.
Storm Hawks: Suzy Lu and the Absolute Zeroes have some of a fanbase, due to their memorable Cloud Cuckoolander antics and taking their Canadian pastiche to amusing levels, while Suzy Lu herself is a rather likeable Cool Big Sis-type character. It helps that the Blizzarians' unique design helps them stand out despite their limited screen time.
Tashy 497, a lovable squishy space squid who showed up in a single episode of the same name, is every bit as beloved as the main cast. His death at the end of the episode is widlely considered one of the most devastating moments in the show.
Xeexi is well loved, considering their 2 minutes of screen time.
Barb, for being a hilariously creepy stalker with zero sense of personal boundaries.
Mirabel. Her popularity may have stemmed from people settling that Ilana was free again because Jason and Mirabel hit it off, even though that was never confirmed.
Todd has become popular due to a stellar performance by an avid RPer who took his little 30 second run and made an interesting character.
Baron from the episode Shadows of Youth. Despite clearly being written as a Hate Sink, he obtained a great deal of popularity, with him often being shipped with Ilana (despite the two never interacting). It's to the point where many wanted him to show up again.
Mike Chan from the episode "Roar of The White Dragon" is well-liked for his self-centered, arrogant attitude and Foe Yay with Lance. His girlfriend, dubbed June, also has a following despite only having a few seconds of screentime.
Meat is also popular for his wacky antics and nonsensical dialogue. It helps that he's voiced by Bill Fagerbakke.
TaleSpin has quite a few One-Scene Wonder characters with fan followings, including cowgirl Clementine Clevenger (Wildcat's Love Interest in "Citizen Khan"), Princess Lotta Lamour ("The Road to Macadamia"), and Adventurer Archaeologists Katie Dodd ("For Whom the Bell Klangs") and Myra ("In Search of Ancient Blunders").
Red X appeared in two episodes where he wasn't just Robin's disguise but has a big fan following, largely for being a mysterious, badass Chaotic NeutralAnti-Villain.
Argent. Despite only appearing for a short amount in two episodes, and subsequently being a very little developed character, there's a large amount of fanart for her, and several fanart groups on DeviantArt.
Kid Flash only appeared in two episodes, but he's very well-liked for being a suave, witty gentleman. Probably helps that he and Jinx became an Official Couple.
Mumbo was said to be a one-off character created for the show, but a positive fan reaction influenced another appearance. Being voiced by Tom Kenny probably helped.
Despite being an original character for the show and having no lines, Kyd Wykkyd has amassed a group of fans for his stoic and mysterious demeanor. It's to the point where he's only surpassed by Jinx as the most popular H.I.V.E. member.
Xever/Fishface is slightly more popular than his partner Chris Bradford/Dogpound, due in part to having a more visually appealing, unique fighting style. It probably helps that the audience learns far more about him than they've learned about his partner.
Spike and Murakami, thanks to being a funny background critter and a Cool Old Guy respectively..
Starting out as divided when people found out about the character Slash is now very well liked due to being portrayed as a cunning, genuine threat who provides interesting tension with Raphael.
Ice Cream Kitty seems to have developed a following, most likely thanks to the mutant kitty being genuinely adorable, especially whenever Mikey's interacting with her.
Tiger Claw has some of this due to being a Badass bounty hunter who puts up a brutal fight with the turtles.
The energetic wrestling announcer/referree/promoter/wrestler Jessica Jaclyn from "Shell in a Cell" has gotten very popular, for reasons that should be obvious. To the point that some fans say her design should have been April's instead. Her performance by Cree Summer helps out.
Boss Bruce from the episode "You Got Served" also has a following within the scalie crowd, likely due to being a handsome dragon.
Taskmaster and Beetle, being both portrayed as badass, menacing and truly competent, got quite good reception amongst the fans;
And so far, episodes involving other key heroes such as The Incredible Hulk, The Mighty Thor or Iron Man got good reaction as well due to being faithful to their most well-known incarnation, especially Iron Man.
Even those who dislike the show tend to admit the janitor played by Stan Lee is an enjoyable part in the show.
Deadpool was a welcome character. Since fourth wall-breaking and shameless comedy have been major parts of his story and character for years, he was received very well. It helps that the episode was written by Joe freaking Kelly. One common praise was the simple fact that he could actually pull off the style of humor present in this show, which many fans hate, feeling that it's out-of-place coming from Spider-Man.
VeggieTales: The Peach only has a speaking role in a couple Silly Songs, but is still a memorable character.
The Venture Bros. has so many ensemble darkhorses that its hard to qualify. Minor characters re-appear as medium character, part of a team or full blown important characters.
21 and 24 (but especially 21 now) are the best example. They started off as nameless henchmen (numberless, too in the first episodes) to have more air time than the Monarch himself. In the latest season, 21, after he Took a Level in Badass, could arguably be called the leader of the Monarchs. The other henchmen refer to him a General 21. He is even putting the moves on Dr. Misses the Monarch, whom he has always crushed on.
Baron Von Underbite, Scott Hall and Radical Left were medium, minor and cameo characters respectively who become part of The Revenge Society.
Scott Hall was a basic yet competent minion who eventually became a powerful super villain who killed dozens of heroes and villains and then joined The Revenge Society.
Shore Leave and Sky Pilot were first shown as OSI agents briefly in a flashback alongside several other OSI agents, and then becoming minor characters for an episode who help Brock escape assassins. And then Shore Leave becomes a relatively important Sphinx agent alongside Brock and Sky Pilot and turns out to have been an important mole all along.
Sphinx and a few of its members appeared in a brief flashback before the good guys revive Sphinx to hunt down bad guys and a few former Sphinx operatives get an entire episode dedicated to them.
The OSI and The Guild of Calamitous Intent were originally unknown to everyone in the cast and were super secretive organizations only heard of in whispers.
The Sea Captain was a one episode villain that is now a reoccurring minor character.
Odlaw from the Where's Waldo? cartoon series seems more well-liked than Waldo himself. To a lesser extent, Woof could qualify as this.
The Heffalumps and Woozles from The Many Adventures of Winnie the Pooh. Canonically, they only appeared in one 3-minute musical segment and were never mentioned again within the film. In addition, they have rarely ever appeared in the Disney Crossovers and for the ridiculously few times that they were, they were just a pass-by Halloween segment or mooks at best! Despite this, they have gained love (and/or terror) from fans of every shapes and sizes due to the segment's love of anything that comes out of a LSD hookah.
Probably the most overlooked character in the whole franchise is Gopher, a character who is very humorous and likable. What makes him so unique is the fact that he was made specifically for the Disney franchise and was not from the stories by A.A. Milne (he even jokes about it by saying, "I'm not in the book.").
Diaspro and Chimera count too, at least in their first appearance when they really looked threatening.
The Wizards of the Black Circle, due to being the most competent villains in the series, and the only ones to permanently kill one of the Heroes. The fan base was pissed at how easily they were defeated.
Daphne is beloved for being a Cool Big Sis, having a unique backstory, and having a really interesting design, though many were upset when her backstory was changed and she was revived.
Dark Bloom is incredibly popular, with far more fan art than her good personality.
Among all the fairy forms, the Enchantix seems to be the most popular, not only for being cute, but also because the requirement necessary to unlock it is a source of development and interesting storylines. Many fan-created original transformations out there are clearly based on Enchantix or include its main characteristics (like having shinier wings, sporting elaborate jewelry, and going barefoot or in some kind of sandals). The announcement that Enchantix would return in Season 8 made fans very happy, until they sawhow it had been changed.
Voice acting wise, among the first Nickelodeon cast, there are those who really like Romi Dames as Musa, mostly from how she sounds very similar to her predecessors get she still adds a bit of spark to stand out.
Le Mime from Xiaolin Showdown only appeared in one episode, but still has his fair share of fangirls, particularly when he's paired with Jack Spicer.
Morph was in the first episodes entirely for the purpose of being killed off so the writers could show how serious the series would be. However, his unexpected popularity led to him being revived in the second season.
Nightcrawler's episode was so well-received they wrote a second one just to bring him back and the writers seriously considered having him join the X-Men after "Bloodlines." Which would have been quite appropriate, seeing as how Nightcrawler was part of the original New X-Men lineup from the 70s — alongside Wolverine and Colossus.
Yuck from Yin Yang Yo! is the evil counterpart of Yin and Yang whose both a Manipulative Bastard and a Jerkass. He only appears in six episodes total throughout the whole series yet that doesn't stop him from having a much larger fanbase than the main characters. Though other villains such as Carl and Smoke are fairly well liked, he is arguably the most popular. His Foe Yay with Yin in "Falling Yin Love" and HeelFace Revolving Door in "Upstanding Yuck" only add on to this.
While people are divided about the characterization of most of the cast, particularly Superman and The Joker, there's one character nobody dislikes: Captain Marvel. He's the most fun character in the cast and seems to be as popular with the fans—and even non-fans—as AQUAMAN was.
The runaways who were experimented on by the Reach (Eduardo Dorado, Jr., Tye Longshadow, Asami Koizumi, and Virgil Hawkins) achieved this after "Runaways". Virgil already had a built-in fanbase, being one of the most hoped-for characters since the show premiered. But Eduardo, Tye, and Asami, derived from Superfriends, have already garnered plenty of fans on their own. That they're all True Companions already helps.
Stephanie Brown. She only has a cameo in "Before the Dawn," and her identity is All There in the Script, but fans were still happy, especially since she was not being used in the comic books at the time. Thankfully, she's set to appear in season three in her heroic identity, Spoiler.
"Coffee Pot Guy", the unmasked manta trooper who offers Tigress a fresh pot of coffee in "Complications".