In Angels & Aliens, to maintain secrecy the Mabba's secret organization forcibly recruits promising candidates. They start by slipping them a dose of nanites that gives them superhuman strength and reflexes — and transforms them into women. (A specific woman, so even if you're already a woman your appearance will change.)
Laura: We can't run want ads — so we find the right person and force them in. They end up thanking us.
In Archipelago one entry in the Listing of Names (a magical book tracking the lineages and whereabouts of the heirs) is garbled and completely unreadable. That's because the person in question has been transformed into a jabberwocky. The transformation is reversed later.
Tuff: The book's magic is too powerful and too unusual for some hex to affect it that much. It must be something to do with the heir.
Yeve the sorceress in Atland teleports her arch-enemy Mael, another sorceress, out into the middle of a desert... then turns her into a fish.
Kavonn turns Oleander Benson into a jackalope, while maintaining his sentience if not his voice, when the Bensons ambush and try to murder him.
When Oleander's sisters track down Kavonn to ask for their little brother back they attack Kavonn as soon as Oleander is returned to his normal form resulting in him turning Oleander and Hydrangea into jackalopes.
When LaBelle and Sadick capture Kavonn he curses LaBelle to shapeshift to become more monsterous or more beautiful in response to her actions. She eventually figures out how to weaponize this.
City of Reality, features the villain Hinto Ama, who wreaked havoc in the World of Magic with her transformation powers. Years later, the Manumitor is a man who seeks to undo the harm she caused by reversing as many of the transformations as possible, but is apparently capable of the same magic. This is because he is in fact Hinto Ama in disguise, seeking to atone for her past misdeeds.
In Crimson Flag, Lord Julian Urocyon found a staff that could transform Reyn into ordinary foxes (Who are still fully sapient, though unintelligible). He tried to use it in a bid for Gray Reyn independence from the Red Reyn kingdom but was foiled by his son Lucian, though both of them were transformed in the process. Lucian and Julian later learn how to use transformation magic on themselves and others without the staff. And eventually it turns out the staff was used by the Reds' "goddess" to uplift red foxes, while a bit of the staff's magic was stolen by a gray fox who became the first Gray Reyn.
In Issue 4 of Deadendia, Pugsley accidentally turns Barney into a dog and Norma into a cat.
Drowtales features Ariel's father, who in the distant past was a dark elf (that is, a surface elf) who was transformed into a giant spider. Ariel's mother, Mel'anarch, has shapeshifting powers. The inevitable occurred. Later on, the bio-mages of the Jaal'darya are able to reverse his condition
In-canon (and out), Grace occasionally gets hit with this trope... but she's a shapeshifter, so it doesn't do anything other than give her a new form to play with.
Erika and the Princes in Distress : The second story arc ends with Pita kissing Prince Aurel; because the way to lift the curse upon him was for a Princess to kiss him, and Pita does not meet this criteria, it doesn't break but instead gets replaced by another curse, and Prince Aurel turns into a frog.
In Goblins, a major battle had several polymorph effects occurring due to the Shield of Wonders. One guard is polymorphed into an ogre, and another becomes a soulspike destroyer. A few issues later, another guard is transformed over the course of several panels into dozens of snakes, which promptly go slithering off in different directions.
Joel, who starts out as a Jerkass, gets transformed while in jail into a corgi by an ancient Sumerian griffon deity by the name of "Pete" in order to serve as his "pet". At first, the audience is led to find this a fitting karmic transformation considering Joel's established personality. However, it is later revealed that Pete didn't do this to force him to become a better person — he wanted to use Joel/King for his own ends in a grand celestial game. Once Joel/King falls in love with another dog and realizes how much he prefers his new life, he decides to remain a dog once he's finally free of Pete.
Thomas Milton, the nefarious and conniving nephew of the late Mr. Milton, breaks into Pete's temple to steal treasure. However, it turns out that Pete placed a protective spell on it, in order to fulfill a deal Mr. Milton made with the griffon, one designed to ensure no that nohumanhand ever touches the treasure (this meaning that all humans who touch the treasure will be turned into an animal)... Thomas learns this the hard way when he looks into the mirror after touching the treasure and sees himself now as a camel. Thomas now has to figure out how to reverse its effects... but all the scrolls he could have used are buried under the temple once it comes down, forcing his camel Sofia to drag him out by his new tail to save him. Whether he'll also find true love and life as a camel to be better than his human life remains to be seen, as it does seem his camel companion Sofia has... a bit of a thing for him now.
It is later revealed that Marion and Lois were transformed at the behest of Steward in attempt to get revenge on Keene by overwhelming his animal equality program with former humans.
Taken up to eleven in recent arcs. As the comic goes on from 2020, it's revealed that more and more humans have fallen victim to Steward's baleful polymorph serial attacks against random people via the cursed temple coin. Seen here is one such victim of Steward's serial transformings. Steward later makes a literal deal with the devil and transforms into a demonic badger unleashing a furry transformation apocalypse upon the entire city.
Several characters in The KAMics have been unwittingly changed into various things. It usually happens to Gertrude & Brunhilda.
New World is largely based on this trope, as both Nicolo and Amanda love turning people into frogs, furries, or anything else comes to mind, usually throw genderbending into the mix as well.
One princess finds a frog in the forest with a sign saying "Kiss Me". She does so, and the frog turns into a bear that immediately mauls her. The whole thing is apparently a practical joke. But she gets the last laugh by bringing a frog, kisses it, and throws it to the pranksters where it immediately turns back into a crocodile mid-air.
Subverted in "Husbandry". A local farmer had been telling the rest of the town that a wicked sorcerer turned his wife into a goat, so when one day a disenchanter shows up who can lift the curse, he is forced to admit that he lied and is really just a goat-fucker.
Vaarsuvius gets temporarily turned into a lizard by a greenhag. However, they can still cast a few spells as a lizard, and every one of them turns out to be useful. Except Hold Portal. They lampshade the trope.
Vaarsuvius: Well, either I spontaneously decided to get in touch with my reptilian side, or I was just the target of a Baleful Polymorph.
In Princess Chroma, the Mentor Mascot started out as a handsome Winged Humanoid with a variety of magical powers and immortality. Now he's a lop-eared bunny at the mercy — or lack thereof — of an ill-tempered middle-school girl.
Princess Princess (2012): Claire plans on turning Sadie into a pig near the end. The spell instead backfires and she gets transformed into one.
In Sluggy Freelance, Torg gave Zoe a necklace one Christmas, having found it inside of an Egyptian pyramid. It turns out to be cursed, and transforms her into a camel. Her friends eventually learn the necklace's history and change her back, but the necklace ends up binding to her in the form of a tattoo, and a pair of magic words spoken by anyone can turn her into a camel ("shupid") or human ("kwi").
Trace Legacy in TwoKinds disposes of his predecessor High Templar by transforming her into a wolf Keidran (anthropomorphic wolf) and having her guards drag her off to a slave market. Incidentally getting polymorphed in the Two Kinds setting is extremely painful. He also gives his ex-girlfriend's annoying little sister thin fur and a set of cat's ears although it's not clear how "baleful" this was as she quite likes the look.
In Exiern, a rogue spellsinger transforms a seamstress into something like her wooden mannequin.
In Dan Standing's Held Within, college student Susie accidentally turns her girlfriend into a genie. When she finds out she has infinite wishes she goes on a spree of transformation revenge, transforming other students into alligator, tree, statue, doll, and other forms..
The Witch and The Bull: This is the basis for most of the quest of the comic as Tan, a rather jerkish royal advisor of the human kingdom, finds himself cursed and turned into a bull without warning. It's only by fortunre that he runs into a witch named Aro who can hear him and agrees to help him out.
This is Princess Thermidora's curse: she was a lobster transformed into a human to remove her as competition for a lobster Baron's heart.
Princess Monika was transformed into a crow after being kidnapped by and evil wizard. Though her curse was technically "undone," she still unwittingly turns into a crow whenever she feels embarrassed or scared.
The Selfish Beast and the Selfless Maiden: Drak was originally a handsome knight until, while he was on a mission to kill an evil wizard, he took a ring from the wizard's pile of treasure, allowing the wizard to transform him into a green dragon. The only way to reverse the effect of the curse was for Drak to fall in love with a selfless woman.
Once the Maiden hears Drak's story, she falls in love with him, but since she took a dagger from his treasure horde, Drak's curse passes onto her, causing her to transform into a dragon too. However, this doesn't stop her from loving him anyway.