In the early BIONICLE movies, the animators took a number of liberties with the characters' appearances, making them look quite different to the toys. In Mask of Light, Gali's figure is less bulky and she now looks more like a Fem Bot. Pohatu is also considerably more handsome there than in his toy form.
In DuckTales (1987) Fenton's mother, M'Ma Crackshell, was a frumpy, middle-aged duck-woman who usually went around in curlers and a shabby bathrobe. In DuckTales (2017), Mamá Cabrera is considerably easier on the eyes.
In Ewoks, a lot of characters were made cuter than in their appearances in Return of the Jedi and the female co-leads were introduced as new characters.
In the film, Wicket was notably shorter than all other young Ewoks (due to having been portrayed by an 11-year-old Warwick Davis). In the animated series, they're all of the same height. He was also changed from being quite clumsy to being a skilled youngster.
In the film, Teebo was somewhat aggressive taller than all the other present Ewoks, wearing an animal skull on his head and a chain of teeth around his neck, his fur black with grey stripes. In the animated series, he sports brown and tan tuxedo patterned fur with blonde fringe and a goatee-like-thing and wears a baggy hat with a feather on his head. He has some magic powers by nature and appears to be shy. And then there was Character Exaggeration in the second season, making him completely different once again.
In the film, Paploo was a smart young Ewok who stole an Imperial speeder bike. In the animated series, he's larger and a couple of years older than his friends and, while he has some badass moments, his bravery is often played for laughs and getting him in trouble.
Face's Music Party: Face looks considerably cuter compared to their appearance in the old bumpers. Their eyes are bigger and closer together, while their mouth moves more fluidly.
Garbage Pail Kids Cartoon: In the movie parody segment "Garbage Pail Aliens from the Junkoid Zone Attack Earth", Alien Ian is featured as one of the aliens, but has a face that is noticeably cuter and less skull-like than how he's depicted on the original trading card.
In the comics, Madame Masque wears her trademark mask to hide her horribly disfigured face. Here, she's a pretty teenager who only wears the mask as part of her Master of Disguise shtick.
Justin Hammer, who was an old man in the comic, but is made a handsome 18-year-old in the show to accentuate his status as Tony's Evil Counterpart.
In Legends of Metru Nui, they even went as far as giving Nokama what can only be described as a robo-cleavage. Seems unnecessary, after they had already turned her ugly toy-mug into a quite nice-looking, feminine face.
Quasimodo is most certainly NOT The Grotesque in The Magical Adventures of Quasimodo. Other than his hunched back (which is very mild compared to most versions of the story), he looks like a normal human.
Zigzagged in The Mask. Lt. Kellaway loses his grey hair, and is depicted as square-jawed and athletic. While he wasn't depicted this way in the movie (which the cartoon takes most of its cues from), this is more in line with his original comics iteration.
In the Mega Man (Ruby-Spears) cartoon, Roll had a body of a fairly curvy young woman rather than the little girl she normally is in the franchise. There's also Mega Man himself, and Proto Man.
A surprisingly subtle example from the Famous Studios Popeye cartoons. In the earliest cartoons Olive Oyl resembles her newspaper comic self but the animators gradually gave her large expressive eyes rather than black dots, feminine eyelashes, high heels, bangs to her hairstyle, somewhat more flattering dresses, and in a few shorts, she actually appears to have something of an hourglass figure◊ as opposed to the 19-19-19 measurements that Bud Sagendorf famously quipped her as having. She didn't exactly become a bombshell but she certainly looked younger, prettier and less severe than the original.
Likewise, Bluto was redesigned, but much more heavily, going from a physically unimpressive Fat Bastard to a muscular Top-Heavy Guy with occasional moments of He Cleans Up Nicely.
Dr. Peter Venkman went from balding, middle-aged Bill Murray to...a thin, 20-something, lanky Hunk with a full head of hair.
Janine, on the other hand, while quite pretty as portrayed by Annie Potts in the films, became a tall, curvy bombshell with a taste for short skirts, big jewelry, and brightly colored clothing. The "Realistic" versions of the 2009 video game decided to split the difference with Janine, by physically basing her on Annie Potts, while giving her clothing the same color scheme as the cartoon.
Varies with Velma in Scooby-Doo, but she gets hit with this rather often. While never truly ugly, Velma was traditionally overweight looking, with a stocky appearance, tacky haircut and a relatively plain face. Starting with Zombie Island, this started to change somewhat, especially in What's New, Scooby-Doo? and the movies (much like Shaggy), where she's made very petite with a tiny waist and an hourglass figure, with a cute-as-a-button face to boot◊. And in the live-action films, she's played by very attractive actresses. The most recent animated movies fuse these two somewhat, and Mystery Inc. also splits the difference – Velma sports a cuter, more stylized version of her original appearance, complete with little bows in her hair. She didn't gain extra weight and freckles until a bit later after the debut so her new attractiveness is a bit closer to how she originally looked.
The redesigns for She-Ra and the Princesses of Power are all over the map as far as attractiveness goes, and appeal (or don't) very differently to different people.
It's hard to deny the new Scorpia (broad, muscular, with a defined upper lip and an undercut) is much more appealing than the original Scorpia (lurid green eyeshadow, sunken cheeks, and awkwardly proportioned claws).
Zig-zagged with Hordak, who is taller, leaner, and has a much more pleasant voice than his 1980s counterpart. His armor is sleeker and covers more of his body than that of the original Hordak. He's also much easier on the eyes than the ugly Hordak of the 2002 He-Man reboot. This Hordak has human-like feet, in contrast to the original Hordak's webbed feet and 2002 Hordak's bird-like feet. However, the 1980s Hordak looked healthy and had an athletic build, while this Hordak is thin and sickly underneath his armor.
In the 1980s cartoon, Imp was a chubby pig-creature. In the 2018 reboot, he looks like a humanoid little boy with light blue skin and bat wings.
In the original cartoon, Horde Prime was an eldritch abomination whose face viewers never saw. In the 2018 reboot series, he's a humanoid man from the same species as Hordak, albeit with some very disturbing features such as multiple eyes, green sclera, and a green mouth, but also notably muscular and is somewhat of a disturbing version of a Long-Haired Pretty Boy, reminiscent of 80s anime.
Sally Acorn from the Sonic the Hedgehog (SatAM) television series is a slightly complicated case. See, the first game featured many cute animal critters rescued from defeated enemies, their names almost all ending in -cky. One of these characters was Ricky the Squirrel, who was given the moniker Sally Acorn (and a corresponding Gender Flip) in western promotional materials. Ricky/Sally looked mostly like a generic normal squirrel; some early promotional comics gave the latter a red or pink bow to offset this slightly, but that was about it. However, when it came time to make the TV series, Sally's design was completely redone, no longer bearing any resemblance to Ricky but instead being a relatively attractive Funny Animal. The comic book took it further; Depending on the Artist, she could either be fairly similar to her TV appearance, or have certain aspects exaggerated to make her an even more attractive, half dressed.
Speaking of Spider-Man villains, Alistair Smythe was a fat, greasy nerd with a messy beard and a receding hairline prior to his transformation in the original comics. In both Spider-Man: The Animated Series and Marvel's Spider-Man, Smythe is thin, clean shaven and reasonably handsome right from the beginning.
The Osborns also often get a heavy make-over in many Spidey adaptations. In Ultimate Spider-Man and Marvel's Spider-Man both Harry and Norman get rid of the weird cornrows they owned in the comics for exchange of more natural looking hairstyles. Harry also gets rid of his weird pointy elf-like features to look more like an attractive (if slightly geeky) kid, while Norman's features are sharpened to look a little more attractive (if slightly threatening).
In the original webcomic Star vs. the Forces of Evil, Princess Pony Head was just as gaudy and sparkley as she is in the show, despite being an actual decapitated horse head, complete with glazed eyes, stuck-out tongue, and viscera leaking from her neck hole. Endless to say, this was cleaned up when being made into a kid's show for Disney XD.
Terra◊. In the source comics she has buck teeth, short fluffy hair, and is otherwise a rather (while exaggerated) "normal" teenage girl. In the cartoon she's petite and has long hair. It's a bit hilarious though, since the cartoon's version of Terra is everything the original hates.
Raven gains a more rounded and conventionally attractive face compared to the more angled one she usually had in the comics, and her legs and overall figure get more of a focus, although again, it's debatable which version ends up actually more appealing.
Jynx is cutened up in the cartoon than in the comics. She is a bald adult Indian woman in the comics (though not unattractive) while in the cartoon she is an ambiguously raced (or even Ambiguously Human) grey colored girl with pink Anime Hair.
In Voltron, Hunk is fat and unremarkable and Pidge is a bit of a Gonk. In Voltron Force, they're both, well, much, MUCH more attractive.
Likewise, Voltron: Legendary Defender makes Pidge rather adorable and gets rid of his Gonk-like features. This is partially because it later turns out that this continuity's Pidge is actually a cute teenage girl in disguise. Haggar is more attractive than her original Voltron counterpart, as especially that with her hood down, she looks like a fairly attractive older woman, helped by the fact that she's an Altean.
X-Men: The Animated Series: The Shadow King's physical form is bald and obese in the comics, but in the show, he is thin, young, handsome, and has a full head of hair.
X-Men: Evolution: Not really "attractiveness," both due to appearance and age, but this version of Leech goes from looking like an alien to a normal kid who's only "sickly green." He's also not a Morlock in this continuity, meaning he could pass (albeit barely) as a non-mutant before we meet him.
Young Justice (2010). Lagoon Boy while he still isn't much to look at, he certainly doesn't resemble some weird, mutated lizard creature like his comic counterpart.
A variation in SpacePOP, where Geela is more attractive in official art and tie-in book art than she is in the show.
The Disney Fairies franchise features Terence, who was a bit scruffy-looking in the books. Pointy, unkempt hair and clothes that looked very thrown together. In the movies, he looks like your typical feminine, non-threatening Teen Idol, with soft, willowy features, clean clothes, and dewey hair.
Static Shock depicts Brickhouse as more conventionally attractive than how she looked in the comics, where she was essentially a female version of Ben Grimm.
In the comics, Deathstroke is usually portrayed as a rugged, one-eyed Silver Fox. Here, Slade is more conventionally attractive thanks to being younger, clean-shaven, and still having both eyes. While he does eventually lose one of his eyes, that still doesn't take away from his attractiveness.
Zig-zagged in regards to Silver Banshee. In the comics, Siobhan, in spite of her face resembling a skull and having a ghoulishly black and white body, is still an Amazonian Beauty dressed in a low cut outfit with thigh-high boots, making her as attractive as a scary monster woman could probably be. Here, she's more conservatively dressed and less muscular, but much more conventionally attractive due to lacking her comic counterpart's monstrous traits.
Depending on the continuity, the comics tend to portray Professor Ivo as either an old man or hideously deformed. Here, Ivo is portrayed as a younger, yuppie-ish man who's outright referred to as "Metropolis' most eligible bachelor". This gets subverted by the end of his debut episode, however, where the effects of the Parasite armor backfiring on him deforms him into a shriveled husk of a man with a blackened eye and Tainted Veins. This then gets double subverted when he's appears again later in a more stable condition. While not as attractive as he used to be, his deformities make him look less like an outright monster like his comic counterpart and more like a normal human with a bad drug problem.
In the comics, the Brain's various mechanical bodies all tend to have a skull motif, as well as being somewhat angular and rather threatening looking. In this show, the skull motif is removed, and the design is far more round and friendly looking.
Mister Mxyzptlk traditionally takes on the appearance of a short, balding old man. In this show, his appearance is that of a young, elfish looking being with a full head of hair, a design that makes him look far more cute than he's traditionally portrayed as.
A lot of Transformers were notably given more humanoid robot modes for the G1 The Transformers cartoon, most notably Ratchet and Ironhide, whose original toys didn't have faces.
in Batman: The Brave and the Bold.
