The rabbit is not just sitting there. The rabbit is part of the monster. So you're looking at an evil tree stump that has a cute bunny on the end of its tentacles so that it can lure people or other animals near it. While I understand the parallel to animals in the real world, I'm still stuck here looking at a googly-eyed tree stump with a rabbit glued to its head. Wow.
Most Shinigami of Death Note are designed in such a fashion. Ryuk and Rem are the most human looking and resemble a winged vampire and a mummy whose arms are vertebrae, respectively, but the others are downright freaky, like Shidoh, who looks like a mummified owl/moth hybrid, or Gelus, who looks like a Frankensteinian puppet made from... other monsters.
Armonia is a skeleton thing either covered or made of gold and gemstones.
Midora is a hominid salamander-y thing.
Nu is a giant rock covered with eyes.
The King of Death is a spherical Eldritch Abomination chained to various surfaces and covered in tree roots made of bone that lead to a skull-shaped structure whose "mouth" contains his actual head... also a skull, but with three eyes.
The ogres probably qualify as well: Bulbous torsos, spindly limbs, and a head that looks like a cross between a sperm whale and a vampire bat with creepily human eyes and a mouth that opens to the collarbones...
Add the fact that they procreate with human women....
None of them can hold a candle to some of the stuff created/revealed when the worlds start to merge with one-another.
This was based on the works of Hieronymus Bosch (see below under Mythology and Religion).
Aratama Tribe: Most of the Oni (former human spirits who mutated into demons that eat negative emotions and produce even more malice) look like their mythological Japanese counterpart: horned heads, sharp teeth, muscled bodies, the usual. The Oni Otoshi, unlike the typical Oni, looks more human and is a pure blood oni that turns living humans into other Oni. One of those humans happened to be a pair of bullied high school students who, under the power of the Oni Otoshi, fused back to back into a bizarre two headed creature with two pairs of hands and legs: http://www.mangafox.com/manga/aratama_tribe/v01/c002/15.html.
Angels from Neon Genesis Evangelion. One of them takes a human form and a few of the others are vaguely humanoid; most of the others are as bizarre as they come. Examples range from giant hovering phallus with laser tentacles to a living sea of negatively charged particles with a three-dimensional shadow.
On a similar note, the Heterodyne from Dai-Guard are similarly bizarre, but have some commonalities. No two are quite alike in design, shape and abilities, but are all based on the same basic composition which is equal parts fungus and octagon-shaped crystal. They then form a body out of surrounding matter, making no two quite alike. They can move freely (some even fly), are usually attracted to EM waves and often have odd powers to defend themselves. That's it. Everything else is up for grabs.
The witches from Puella Magi Madoka Magica. On the normal end of the scale you have a human-shaped silhouette that attacks by growing a tree at it's target. On the weird end there's a giant monster made of skirts and arms. The others fall somewhere between.
Many of the creatures and plants in Toriko. Especially the ones based on normal foods.
Pick any youkaiof the week in InuYasha readers are bound to find this trope, including bird monsters with upper human bodies attached to giant furry balls of teeth with wings, a sickle armed white...thing with a Bishōnen head that is an offshoot of the Big Bad's body and lives inside the intestines of its human-looking younger brother like a parasite, a spider demon who masquerades as a kindly monk but whose form is actually a GIANT FLESHY SPIDER WEB, a hair demon whose true form was a red comb covered with hair entangled with skulls, two conjoined-at-the-waist yokai who fight for control of their body, and a giant dragon that would look indistinguishable from any other dragon if it were not for the talking mask on its forehead which is it's real face.
In With Strings Attached, Brox develops a spell that turns random bits of inorganic trash into living creatures (which the four dub Nasty Bits). They encounter such delights as a boulder with tentacles, a spidery glass-thing, an animated statue of a god with a penis as long as its leg (and using it like a sword), and feet (broken off statues) that hop around, prompting George to mutter “ Monty Python, Monty Python.” Also, Ringo's pair of black opaque glasses comes alive and scuttles out of his beltpouch.
Paul later learns how to actually make these things himself. He loathes the spell, but it comes in handy once.
Films — Live-Action
Ghostbusters, in all media. Although the trope doesn't really kick in until The Real Ghostbusters, signs of this still creep through in the original movie—the Squid Ghost is one, and there was another idea in which the Stay-Puft Marshmallow Man would become something truly monstrous in the final battle.
The popular consciousness' conception of Mothra fits. As Big Creepy-Crawlies go, butterflies are pretty tame. Then you find out that she's a god or other supernatural being related to protective goodness, things make a whole lot more sense—or get even more confusing. Either / or? Not weird. Together: Weird. The fact that she's the only monster to have a consistent string of victories against Godzilla says volumes for her prowess. A lot of Japanese monsters tend to fit into the "weird" category.
Gabara, however, certainly falls under this. He's an oni-like (Oni are essentially a Japanese equivalent to ogres) monster who basically exists to bully Minya, and it's implied that he's nothing more than the result of some kid's overactive imagination. Also... he looks like a cross between a cat and a toad.
To an American, King Caesar makes no sense whatsoever. The trick: it's actually "King Shisa", a Shisa; an Okinawan variant of the temple-guarding Chinese Fu-dog. Why it has scales is anyone's guess, though other parts such as the crystal, energy-beam-reflecting eyes hint at its golem-like nature.
The Dorats. Cute foot-tall lizard-bat-cat things that are basically genetically engineered...things...created to be the "perfect pet". That is, Until they are exposed to radiation from the SAME atomic bomb that creates Godzilla and become King Ghidorah. It's a case of three weird-looking small monsters merging into one HUGE weird monster.
Gigan AKA The Cyborg"Space Chicken". With hooks for hands (chainsaws in one film) and a buzzsaw on his stomach.
Megalon certainly counts. He's a giant bipedal beetle god-monster with drills for hands! He spits napalm and shoots beams from his antennae.
There's Destoroyah who happens to be a giant demonic-looking creature who's also billions of tiny crab-like monsters merged into one entity of pure evil. Its like Hedorah, but made of little crabs instead of sludge.
Spacegodzilla, a giant alien clone of Godzilla with huge crystals growing out of his shoulders.
While neither of these monsters have appeared onscreen with Godzilla, Maguma and Bagan have found their way into the fans conciousness. The final product  was considerably different, but the original concept of Bagan was a dinosaur, a bird-monster, and a fish-monster that would then combine together in a final form. Maguma was a giant walrus.
Then there is Tabonga, the s-l-o-w-l-y walking killer tree-stump of From Hell It Came.
Better yet are the monsters from the Filipino "Blood Island" series, plant/human hybrid that take forms varying from a recognizably human "chlorophyll man" to a giant man-faced running tree who dismembers women out of frustration because...well, he's a tree now, so he can't do what he really wants to do with them.
Guiron, as well. For Pete's sake, he's got a huge freakin' knife growing out of his head!
Growing out his head? Hell, he's got a huge freakin' knife for a head!
Zigra is a giant goblin-shark monster from another planet. Oh, and he's one of the few monsters in the Gamera films that can talk.
The Silicates from Island of Terror are some of the most bizarre monsters of all. Small, starfish-like creatures with mouth on the end of along tube. They are covered in a thick calcium based shell which makes them well armored. They feed on calcium by injecting a dissolving fluid into a victim and sucking up the liquid goo leaving behind the flesh and organs untouched. Even better? They divide every 6 hours.
The Masters Of Horror episode "Deer Woman", about a vengeful Native American spirit who seduces men in the guise of a beautiful woman, then tramples them to death with her powerful deer legs.
The Green Slime: Alien monsters with rounded heads, no shoulders. Cyclopean, they have tentacle arms that end in pinchers and 2 feet ending in tridactyle claws. They are Psycho Electro and eat energy. If cut, their blood can grow into new ones. Their touch is lethally electric and they can use that energy in their claws to seal any wounds. Strangely, regular fire kills them fine.
Ro-Man, a gorilla wearing a space-helmet. Notable especially for having somehow or another murdered all of humanity, save six people.
Parodied in Family Guy when King pitches a lamp monster as the latest scary thing.
And in Full Frontal Nerdity, with a bloodsucking radio. That has to be killed by singing "Achy Breaky Heart".
In The Taking by Dean Koontz, the devil is portrayed as a colossal organic spaceship with control over enormous storms tearing up the entire planet. There are also walking fungus monsters from Hell, and other, unseen monsters that seem pretty strange.
Walter Moers's Zamonia books are filled with strange monsters. These include giant insectoids with a kazillion suckers, crystal scorpions, an army of cyborg robots and cyclops with spines in their tongues.
In Chris Evans The Iron Elves trilogy among the Big Bad's minions are black, blood-sucking trees. In the third book a few of them feed from buried dragon eggs. Some of them learn to walk, grow arms and become explosive when shot. They also can throw fireballs. A pair grow wooden wings and claws and essentially become tree-dragons. That's right folks, flying trees.
Discworld has the occasional one-off joke about some of the weird monsters that have evolved on the Disc, like the shadowing lemma, a two-dimensional creature that eats mathematicians, and the .303 bookworm, which is designed to burrow very quickly through magical tomes.
The thing on the cover of the first book on this page. It's like a cross between a porcupine, a hammer, and one-and-a-half people.
John Dies at the End: Some of the creatures envisioned in this story are truly bizarre - such as the "Wig Monster" that looks like a dog-sized scorpion, with 7 chubby babies' arms for legs, a parrot's beak for a mouth, an empty space where a waist should be, and a toupee very obviously held on with a rubber band. And this thing is almost played for laughs; the ones that aren't truly bizarre, are bizarre and unbelievably horrific....
The Cogno series has a massive array of these oddities, although it's somewhat justified since they're aliens. Just among the protagonists, pretty much all of them are utterly bizarre. It says something when the least strange one is a three-eyed cyborg (Volo).
Cogno, the eponymous character, is a Faceless Eye connected to an orange stalk with a small mouth and four tentacle-like feet. He also has two orange tendrils on top of his eye.
Scribo is a robot with a head shaped like a pen nib and a four-legged, trapezoidal base.
Phonica is a snakelike pink elephant with two trunks and three stalk eyes. She also has a photographic memory and can speak in dozens of languages at once.
Chrono is probably the strangest one- he's a bulky Armless Biped made of twisted red-and-blue tentacles that is capable of Time Travel.
Undula is the Last of Her Kind of a spacefaring race of bluegreen-and-yellow serpents capable of faster-than-light travel.
Quaestor has five legs and four eyes (one pair is large and the other pair is stalked), and is also the galaxy's best detective.
The Gemini Twins are a pair of orange seahorse-like Planimals with Psychic Powers. They also cannot talk, since they have evolved telepathy over anything else, so they rely on Cogno to speak.
In Jack Campbell's Lost Fleet series, humans deal with an alien race that are a revolting, nightmarish combination of spider and wolf in appearance — all the more oddly in that their aesthetics, judging by the colors of their clothing and their elegant spaceships, are similar to human. Despite the impeccable graciousness of their behavior toward humanity, many humans are outraged that the fleet allied with them to fight against teddy-bear-like aliens, even though those aliens immediately attacked without responding to any hails.
In Andre Norton's Catseye, Troy finds the hur-hur revolting and alien in appearance, even a wrongness in its form. Only the prospect of facing hunger and unemployment again lets him even stand carrying the case that holds it. Citizen Dragur, in contrast, is greatly enthusiatic and even calls it beautiful.
A good deal of Tokusatsu monsters fall into this category. Many fit standard tropes, but every now and them something really WEIRD shows up.
Ultraman and many other entrants in the Ultra Series have a good deal of weird ones. The ones that stand out include: Prisma (a giant crystal monster); Buluton/bulton — extra-dimensional coral head which warps reality around it with TV antennae and egg-beaters that sprout from its polyps; the parakeet-headed Gutz; Lunatyx the rabbit-headed lizard with a fluffy tail and explosive eyeball launchers; The backwards upright fish alien Metron; and Dada — a monster based on the art movement (No, really!).
Chojin Sentai Jetman specialized in turning objects into monsters—a pachinko machine, a hair-dryer, a drink machine— and later combined them randomly with animals, creating things like "Spotlight Armadillo" and "Hammer Chameleon."
A lot of Doctor Who monsters probably qualify, but the Kandyman deserves special mention—a psychopathic torture robot literally made of candy.
The Adipose are Ugly Cute little monsters made from human fat.
Buffy the Vampire Slayer and Angel use this trope more an more as time goes on. It gets to the point where you have demons that make you just want to yell "Why can they do that!?" or "Why do they look like that!?". Clem is a perfect example. Why does he have dog ears? Why the weird skin? What is his true form that we never really see? Does it have any real uses at all? Is there a point to his continued existence? Or, to sum it up, "Why?"
Farscape managed quite a few of these as one of its goals was to showcase the work of the Jim Henson Creature Shop.
Special Unit 2 was all about this trope. Besides the basic creatures (gnomes for example), just about every Link is some weird, unconventional monster. Like the Barney the Dinosaur expy who was the inspiration for The Pied Piper (his plush felt "costume" is actually his body) and the creature made entirely of human fat.
Billy the Mountain, title character of Frank Zappa's epic length song, a walking, talking mountain whose wife, named Ethel, is a tree growing off of his shoulder. He's also a draft dodger.
Mythology and Religion
Well, wouldn't the tanuki qualify for this, seeing as one of their defining characteristics is their massive nutsacks? Which I believe have been shown as bludgeoning weapons in the movie Pom Poko.
Incidentally, the massive scrotums are an exaggeration of a property of actual tanuki.
Angels. When they did not appear as ordinary humans they had 4 wings and the faces of a man, a lion, an ox, and an eagle (Cherubim); 6 wings and are covered in fire (Seraphim) or are giant glowing wheels covered in eyes (Thrones). Even when human in appearance the first thing someone did upon discovering they were with an angel was to freak out. When they showed up in one of the aforementioned appearances the greeting was usually "fear not".
Of course, demons could also get pretty weird too. Try looking up Bael, Asmodeus (Not the D&D version) and Decarabia, who appears as just a floating pentagram.
Keep in mind that these creatures have no corporeal/earthly forms - what with being beyond the physical world and all - though angels did have the ability to appear in human form in the Bible, and demons had methods as well.
For many westerners, the Kappa (imp with a hollow space filled with water in its head) fits into this category, if just for the really dumb weakness (if the water falls out, it loses its powers; it bows if you do). Also, Kasa Obake, the one-eyed, long-tongued umbrella spirits.
The Japanese were all over this: women with insatiable hungry mouths hidden on the backs of their heads; tapirs that eat dreams; invisible walls; giant feet that crash through ceilings; even gianter skeletons made of regular-sized skeletons; the angry little dude assembled out of a ceramic tea-set; and my personal favorite, inanimate objects, if not taken care of, become animate after a hundred years or so, with popular examples being the umbrella, the paper lantern, the straw sandal, the koto...
Rabbit crossbreeds seem to be popular in world mythology, for some reason. A few examples:
The Jackalope, an alcoholic jackrabbit with antlers that can mimic human voices.
The Wolpertinger, a winged jackalope with duck feet that faints when it sees breasts.
And suddenly Anya's fear of bunnies makes perfect sense.
In the Hindu epicRamayana, one of the level bosses—come on, it might as well be a video game—was Kabanda ("Barrel"), a huge torso with a mouth on one end, ringed with sword-wielding arms. It turned out to just be a good-guy demigod that had been punched in the head so hard it got mushed into his torso and turned him evil; once the heroes defeat it, it returns to normal and joins their party. (See? Video game.)
The Jersey Devil. It's a type of kangaroo... bat... horse... cow... human... demon... thing... it's kind of hard to describe, as you can see.
The Jersey Devil's cousin South of the Border: The Chupacabra. Nobody can quite agree as to what ol' Chupy looks like. Some sort of lizard-monkey with dorsal spines and red glowing eyes? Something that looks like a coyote crossed with a naked mole rat? A demon with bat wings and vampire teeth? Just about the only detail anyone can agree on is that it sucks the blood out of farm animals.
The Philippines features quite the Rogues Gallery of strange and almost always homicidal mythological beasties. The most famous is probably the Manananggal, a vampiric creature that Eats Babies and can fly by separating its torso from its legs. Additionally, there's the Tiyanak (a vampiric baby that died before it could be baptized), the Kapre (a Sasquatch-like figure that guards people but also likes to play tricks on them), the Alans (mischievous bird-humanoids that like to take care of lost or abandoned children and have backward facing hands and feet), the Bungisngis (cheerful but dimwitted cyclops-like giants) and the Aswang (a frightening, shapeshifting predator).
Mortasheen takes this trope and it runs with it for pretty much every monster in there.
The flumph is infamous in Dungeons & Dragons circles.
The 1988 module Castle Greyhawk had the Plane of Silly and Unused Monsters, a dimension filled with all of the bizarre and stupid monsters that TSR had created up to that point. It included the flumphs and modrons already mentioned, and many more.
The duckbunny. Its original Monster Manual explains that if you are going to be an evil wizard that makes bizarre hybrid monsters, you had best start out with something that is utterly harmless, lest it turn on you.
Speaking of Dungeons & Dragons classics, Gelatinous Cube (yes, it's a moving cube of transparent gel), Cloaker (cloak that bites... with its face).
And don't forget about the Acosmoid, a gigantic fungal ball covered in holes that attacks by ramming you.
Also, we hit 4e and standard monsters are suddenly breaking their own rules, like Dryads not having that tree dependency thing any more. Also, redesign Dryad from D&D 3.5e◊ and then the D&D 4e version◊; less pretty, more mobile.
Then, there are Lava Children from 1E who were "immune" to metal (it just went right through them), sported chimpanzee-length arms with scything claws, and sported a permanent cheerful grin.
Nearly the entire monstrous cast of the classic "Expedition to the Barrier Peaks" adventure was Gygax deliberately messing around with this trope.
Then there's RuneQuest, with its intentionally unorthodox setting taking out most of the "normal" monsters you'd expect to find in a fantasy setting and going beyond DND stupidity levels instead. Highlights include: the Duruluz (duck-people), the Gorp (which amounts to an giant acidic living booger), the Jack-O-Bear (a bear...with a jack-o-lantern on its head), and the Walktapus (an octops with legs).
Even their version of the Five Races is weird: elves are a type of plant, dwarves are machine-like, trolls are an ancient and dying culture, and some humans are non-sapient and hunted for food by the tapir-like Morokanth.
The "monster the DM made up himself" from Munchkin. It gets + 2 on a Saturday, among others.
In Low Life, most of the monsters fit into this category, but a special note goes to the Cremefillians who are basically freaking Twinkie-men brought to life by the pollution from the Apocalypse and bitter towards the long-dead hyoomanrace for eating them back when they were non-sentient. And the best part? They're a PC race!
Mage: The Awakening applies this tendency to creatures of the Abyss, on the general principle that if you think "monsters from outside reality" are just "squamous things with too many tentacles," you're not thinking big enough. A formula that represents the physical laws of hell and rewrites reality around it! A contagious form of aphasia that takes the hallucinatory form of an angel! An alternate history aborted by reality itself that has twisted inward and turned cannibalistic!
In fact, when the New World of Darkness wants to do wandering monsters, it does this a fair amount of the time. Some good examples include the things lurking in the Hedge (one piece of fiction has a changeling pursued by a ventriloquist's dummy with a few human parts, armed with a camping hatchet) and the entities of the Underworld (it says a lot that the Geist core book makes mention of one of the few Kerberoi that have anything approaching a humanoid shape, and even then it looks like something out of Hellraiser).
Gamma World has this trope nailed for most of its monsters, like the winged mandibled lion who has laser eyes and eats fabric, or the bunny-men who turn stuff to rubber. And let's not forget about the Pineto, AKA the cactus horse!
The kami from Kamigawa block, which includes the picture at the top of this page, have them beat. The tame ones are faceless humanoids with elongated limbs. The really weird ones might take the form of a flying mass of coral covered in mouths.
Genius: The Transgression: leaving aside the ones you can grow in vats, the things a moderately inquisitive Genius can find include stuff like culturally Hispanic goblins made out of paper, and pixies spawned from failed equations. Then things get weirder
The Splinter: Monster in The Splinter are one part traditional fantasy creatures put through a weirdness filter (Living Avalanches instead of Earth Elementals), one part creatures that would make sense in other genres but are shockingly strange in a fantasy dungeon crawl (Cats of Ulthar, Robotic Attack Drones), and one part truly bizarre (humanoid, chitin-covered bio-weapons that can integrate found technology directly with their bodies; clockwork, parasitic hummingbirds.)
Dreamblade includes a plethora of weird monsters, mixing and matching elements of fantasy, science fiction and horror in their designs.
Exalted dives into this trope whenever dealing with the denizens of Malfeas. At the top of the food chain, you have the Yozis, who take forms such as an endless silver desert, a constantly shifting city, a silver forest, a carnivorous swamp, or a typhoon of emotionally-intoxicating rain. And then you have the demons under them - many of which are their own numerous souls - who take forms such as a brass forest, a quicksilver highway, or a contagious and eventually lethal emotion.
BIONICLE's wildlife. Just a few examples: Tarakava are said to be water-lizards, but they stand upright, have huge tusks, enormously long punching fists, and tank-threads for legs. Muaka and Kane-Ra are a tiger and a bull respectively, but they have dinosaur-heads, extending necks and also have threads. Nui-Rama are gigantic insects with large teeth and clawed arms. Manas are crabs that resemble tanks with pincers. The Rahi-Nui is made up of all of these, plus a scorpion. Gukko are large birds with four flipper-like wings and no legs. Just click through thegalleries. Some are fairly familiar-looking, others are near indescribable.
The Guardian Legend for NES has some pretty strange enemies, especially for a sci-fi shooter-hybrid. Giant lobsters, eyeballs that shoot sea-weed walls, color changing spiders that multiply exponentially if you don't kill them quick enough, and don't forget the three-eyed final boss!
A proud tradition of the Shin Megami Tensei meta-series, thanks to the fertile (and twisted) imagination of artist Kazuma Kaneko. The fact that all the monsters are drawn from real-world mythologies - which, as you can see above, have thought up plenty of truly bizarre creatures - helps too, but Kaneko manages to make even mundane-sounding deities weird and creepy.
Morrowind's silt striders (giant walking flea things) and netches (giant insectoid jellyfish creatures that drift around the sky looking menacingly beautiful). It has some other weird monsters too.
Garchomp is a torpedo/shark/dragon hybrid. Its head is torpedoes.
Shuckle is a barnacle. However, this is still fairly bizarre, because it's a barnacle that has evolved to live on land and feed by allowing fruit to ferment in its shell.
Sableye, a weird little gremlin ghost that lives underground and... eats rocks. Because its eyes are made of diamonds and it wishes them to remain so.
Deoxys. It has tentacles and it shapeshifts. And is a space virus mutated by cosmic rays. And its three original formes (Defense, Normal, Attack) anagram to DNA.
Tropius. It's a fusion of a sauropod and a banana tree... that can fly. And it grows bananas on its neck because that's apparently what it always ate.
Eelektross, an oversized navy-blue electric lamprey... thing.◊ That floats over land.
Claydol is a floating black statue thing with eight pink eyes and cannons for hands. It also has psychic powers, for some odd reason.
Pokémon includes a walking tree with multiple psychic heads note Exeggutor, a haunted cicada exoskeleton note Shedinja, explosive balloon-like smog creatures which fuse together note Koffing and Weezing, giant magnetic moai heads note Nosepass and Probopass, snails made of hardened magma note Slugma and Magcargo, psychic punching bag creatures note Wobbuffet, water-mammals who share brains with parasitic seashell creaturesnote Slowbro and Slowking, a large blue monster fused with a pipe organ, note Exploud and whatever Swalot is supposed to be note A giant stomach..
And with the new Generation V Pokémon, it just gets even weirder. Like the ice cream cone Pokémonnote Vanillite family, the coffin Pokémon,note Cofagrigus the embryo Pokémon,note Solosis family, a giant floating snowflake, note Cryogonal a pink tapir with a plume of pink smoke coming from its head, note Musharna and mushrooms that look like a Pokéball for no reason.note Foongus and Amoonguss Also, have fun guessing whatever Sigilyph is supposed to be.note It's the Nazca Lines Hummingbird. To complement the toxic waste note the Muk family and stomach Pokémon, there's now a trash bag Pokémon.note Trubbish
Then comes Generation VI, which includes such oddities as a giant draconic bat with stereo speakers for ears, note Noibat and Noivern a red-eyed purple seahorse that looks like seaweed, note Skrelp and Dragalge a possessed floating sword that unsheathes itself with a hand-like tassel, note the Honedge family the cotton candy Pokémon that becomes a cupcake dog, note Swirlix and Slurpuff Cthulu-esque bioluminescent squids with the power of reversing things, note Inkay and Malamar a humanoid collection of barnacles, note BarbaracleBlob Monster dragons, note the Goomy family and a sentinent key ring. note Klefki
Even the legendaries get bizarre sometimes. There's a psychic cat fetus note Mew and its purple humanoid Super Soldier clone with a giant purple tail, note Mewtwo a time-travelling onion pixie, note Celebi psychic brother-and-sister dragons which look like fighter planes with arms, note Latios and Latias a giant shape-shifting ghost-dragon-centipede thing, note Giratina a floating psychic moon swan, note Cressalia a pair of cliones, note Manaphy and Phione (disputed) and a giant white armless centaur with golden wheels attached to its torso (which is also God. note Arceus
And that's not even getting into the countless Fakemon thought up by fans essentially on a daily basis.
Wario Land has a few of these, although the King Bubble thing from Wario Land 2 (which is a giant, evil water bubble) and Cuckoo Condor somewhat come to mind here.
And Wario World has some really, really weird bosses. There's the clown that tosses his detachable heads at you, and whose real face is on his stomach, a giant-headed ice spirit-child thing that breathes ice, a giant chess piece, the giant green dinosaur that wears a bikini, lipstick and jewelry, as well as having long, blond, wavy hair and so on.
The Super Mario Bros. series is pretty bizarre. Goombas are evil mushrooms; there are turtle-goblin ninjas that throw hammers, and at one point a giant toad that burps bubbles, defeated by force-feeding him vegetables.
EarthBound has a ton of enemies that don't make sense. They have a blob of vomit, a man made of balls, a ball Made of Explodium that keeps smiling, and Giygas, a red, swirly, skull-fetus... thingy... and his alien minions.
Monster Rancher is a mon game with a huge variety of creatures to train and battle with that vary from being based on Japanese myth to fantasy-tale creatures to robots to... things. Tri-segmented wind-up ducks, rhinos riding on wheels, clown-faced caterpillar triplets, humanoid shape-shifting blobs with the face of Scream, mole-dogs wearing giant pointed hats. Hell, the very mascot of the series is a yellow, comma-shaped monster with only a big eye, almost as big mouth, and a tail that it stands on. All of this is even worse when you consider the possibilities that can be made when combining monsters. Golems with a goofy smile for a chest, giant beetle monsters with duck heads for a horn and arms, a giant blue-skinned camel-elephant with a joker-smile, a multi-colored humanoid jell with the colors of a little girl in a kimono... Jeez, this goes on. Over 328 of these guys exist, and a big chunk of them could easily stand-up the current trope image in surrealism.
JRPGs are full of really, really weird monsters. They can be even worse than Dungeons and Dragons.
The final boss of Persona 2: Innocent Sin. It is literally a tentacle monster made from the fathers of the protagonists in bondage gear.
The final boss of Eternal Punishment is obviously Lovecraftian with a crapton.
On the subject of Persona... the true forms of the shadows in Persona 4. Other than Naoto... FREAKY.
A lot of stuff drawn by Tetsuya Nomura is rather quirky. Even some of the monsters in the games where he was a debugger or minor monster designer.
Some stuff done by Amano is pretty interesting but it isn't quite as freaky compared to Nomura's almost mind screwy Noise and Heartless. Or Ultimecia. ('Course, he didn't design 'everything).
The Heartless from Kingdom Hearts tend to be weird, such as the Trickmaster boss from the first game, anthropomorphic cartoon cars, demon dogs, walking gumball machines with teeth... the list goes on. Possibly the strangest is the Final Boss, who starts off human(oid), but has a bizarre One-Winged Angel form. Y'know, the one where he's a freaking boat with his old humanoid torso, arms, and head sticking out and ALSO the stage you're fighting on! And that's not even getting into Nobodies, Unversed and Dream Eaters!
Shadow Hearts loves these. The most notable are the Police Dog and Mailman, dogs with human arms coming out of their faces (which they balance on). Then there are the ones that, in any sane world, would be arrested for sexual predation...
The Gentleman monsters in the Tales Series are featureless humanoids that sometimes wear dress suits (As the name might imply), the hats of various Tales characters or even the hats of characters from other Namco games. Their attacks tend to be no less weird, consisting of things like bowing, running through the air, and swimming across the ground. Despite their weirdness, they're usually very dangerous compared to run of the mill monsters, and some are optional bosses.
The Freeware RPG "Middens" has monster portraits that look like what might happen if Salvador Dali painted in the style of Leonardo da Vinci while on drugs. Special mention goes to the skeleton womb nursery car.
The good ol' Half-Life series still has some of the weirdest aliens in gaming history. Let's take a tally of the monstrosities encountered by Gordon Freeman:
Headcrabs, little Puppeteer Parasites that latch onto your head, devour the brain and mutate the body into a nightmarish Zombie. The bottom of the food chain, most die before reaching maturity: a massive, armored Gonarch, a "testicle-on-spider-legs" that spawns other crabs by the dozens.
Houndeyes, three-legged dog-like things with massive compound eyes that hunt in packs and attack with powerful sonic waves. They seem to feed like spiders, by dissolving the prey before eating it.
Bullsquids, fast, vicious predators hostile to almost everything they see (including, occasionally, others of their kind) that spit poison at long distances and can beak a man's legs off with a swing of their tails. Characterized by the multiple tentacles arranged around the maw. Will try to eat or mate with almost anything. Seems to hunt Headcrabs.
Barnacles are... growths on the ceilings that form a mouth rigged with sharp teeth. "Prey" is anything that happens to touch the sticky tongue hanging from the mouth.
Vortigaunts/Slaves, Grunts/Soldiers and Controllers/Masters form what seems to be a civilization of sorts; the species are obviously related to each other. Characterized by breathing tubes on the sides of the head, vertically-opening mouths, multiple red eyes (three or five), hooved legs and a third arm on the chest. The Vortigaunts and Controllers can manipulate electricity, while the massive Grunts use a biological rifle that spawns and launches small, vicious homing insects.
The Gargantua... is best described as a massive bipedal tank. It's beetle-like armor is impervious to small arms fire, and even explosives have a hard time going through. They have four arms, of which the upper two can be user as devastating flamethrowers. The animal is likely full of fuel, and goes off with a huge bang when filled.
Tentacles are somewhere between a plant and an animal. Massive, snakelike monsters that usually emerge from pits and kill anything around it. Blind, but very sensitive to ambient sound.
Half-Life 2 introduced the Antlions, eusocial insectoid aliens that seem to have thrived on Earth. They come in three varieties: basic Antlions are the size of a tiger. Myrmidonts or Guardians are about the size of an SUV and are very hard to kill. The Workers usually reside underground and can spit an acid that they use to dig through rock.
Silent Hill monster Pyramid head. Even if he isn't as weird as others, I'm sure Freud would like to have a word with him...
All of the monsters from the series fit this trope, except for the very traditional looking demon at the end of Silent Hill Origins. There are, among other things that are all horrific, monsters wearing straitjackets made of their own skin, a woman in a cage with her mouth locked in a perpetual scream, and a nine foot tall doll with porcelain armor and soft, bloody insides. None of these fit normal monster categories very well, but they are all absolutely freaking disturbing, and all of them are out to kill you.
In general, abominations made from the twisted psyches of highly disturbed individuals (e.g. Alessa, James, Claudia, Walter) will result in this trope.
One boss in Ape Escape 2 is Yellow Monkey, a member of the freaky monkey five. While the other four members look like monkeys in the game universe, Yellow Monkey looks more like a gigantic rubber duck crossed with a sumo wrestler than an actual monkey.
The Dragon Quest series has some (intentionally) silly (but still dangerous) creatures, including shish-kebob monsters!
The eponymous Metroids are floating jellyfish with teeth that will suck out your life. If left alone, these jellyfish turn into flying dinosaurs that spit fire/lightning (no ice,for a very good reason). From the same series comes the X, which are floating piles of viral stem cells, and the Ing, which are five-legged spiders that specialize in Demonic Possession.
Other enemies in the games are often weird, weird things. From super-fast sea serpents to walking tree monsters that can Spindash to plants that shoot plasma and who-knows what else.
The Prime series, aside from the aformentioned Ing, has giant lava clams, a mutated praying mantis plant, tusked rock toads, a bisected shark-like creature that is held together by electricity, trilateral armored squids whose solution to everything is ramming into it, flying plants that turn invisible and shoot sonic waves, teleporting dogs, and pretty much everything on Phaaze.
Other M is the most notable. It's got giant purple chameleons with huge tails, oversized humanoid armadillos, six-legged tree dinosaurs that can flip over and walk upside-down, explosive worms that wear horseshoe crab-shaped Powered Armor, a bipedal frog-whale with antlers, a giant lava monster with flailing limbs and devil horns, huge dinosaur-like creatures whose posterior is a giant mouth, giant growths on the ceiling with one huge eye and a centipede-like extremity, a gravity-controlling box-shaped thing that wears a mask, what appears to be a fusion of an alomocaris and lemur that is capable of flight and firing rockets, and cyborg humanoid beetles that act as door locks.
La-Mulana has not only "Catball" (a cat balancing on a rolling ball), but a Mini-Boss which resembles a ball with lots of holes in it with snakes coming out, and a monster which keeps throwing its innumerable eyeballs at you and appears to be made of nothing else.
Dwarf Fortress has randomly-generated titans, their subterranean variants, forgotten beasts, and their Hidden Fun Stuff variants, demons. One generated during testing had the body of a giant shrimp, covered in bright purple fur, with a long elephantine trunk. Another was a giant lime-green crow with huge mandibles and three eyes. Once the version was released, it just got weirder from there. They can even have features of animals that don't currently exist in any other capacity of the game. The weirdness is increased by the way the game announces the monster's full physical description to you when it appears. You get a box appearing in the middle of the screen to tell you, for example,
"The Forgotten Beast Bisek Nirurnokgol has come! A towering feathered leech. It has wings and it has a gaunt appearance. Its scarlet feathers are patchy. Beware its noxious secretions!"
Angband and other roguelikes, given that they don't depict creatures visually, are free to have all kinds of bizarre monstrosities. Browsing through the monster files of those can be quite an experience for someone with a vivid imagination. For instance, in Angband there are quylthulgs, pulsing mounds of flesh that defend themselves by summoning other monsters.
Castlevania got into this territory after it moved into Metroidvania games. A lot of the monsters are very accurately modeled after demons from the Lesser Key of Solomon... which, as noted above, means they're going to be odd by default. But that doesn't quite justify the bird-riding fleamen, Ninja Maid squads, or skeletons with Kamehamehas.
Mirror of Fate has the gigantic insect-dragon known as the Lady of the Crypt. The slime-ghost-like "Lady" is actually a lure on the dragon's head that it has developed to lure human prey, and is even capable of attack! Unfortunately for the dragon, the lure also seems to be its weak point.
Arrghus, the giant eyeball in a floating jellyfish surrounded by little cloud monsters with eyes.
Wart, the gian
Barinade, the hideous flesh-pile covered in electrified jellyfish topped with three tentacles that end in rayguns.
Bellum, some kind of flying jellyfish/eyeball/tentacle thing.
Blizzeta, giant flying Russian doll made of ice, and a funny, fuzzy blanket-ball in the middle.
Bongo Bongo, the huge phantom monster that looks like an upside down armless torso with a red eye where the head should be with 9 yellow pupils and six eyelids that open up like flower petals, and has a pair of massive floating hands that constantly play a huge bongo drum (which is also the fighting arena).
Digdogger, a giant bouncing blob with a massive eye in the middle.
Facade, which is both the boss and the floor of its own boss room.
Goht, a robot bull (not a goat) with an old man's face which fires lightning from its horns and throws bombs at you.
Kholdstare, the pink fluffy cloud with a single eye (Zelda likes its boss monsters with huge, singular eyes) that starts the fight encased in ice.
Vitreous, which is yet another giant eyeball, this time in a pool of corrosive... stuff, surrounded by other, tiny eyes which fly at you.
Scaldera, a giant six-legged, one-eyed ball of magma encased in rock.
Tentalus, a sea monster that looks like an overweight man with dreadlock-like tentacles for "hair" and a single eye.
Molgera, a giant Sand Worm with a head that looks like a manta ray, but with a mouth that opens down the middle, that can fly and also brays like a donkey when damaged.
There are MANY more (peahats, Majora, etc.), but the above list should be enough to give you an idea.
The Legendof Zelda CDI Games have Harlequin, an anthromorphic pig gambler; Omfak,a... demon? that shapeshifts heads between a wolf, a fire breathing lion, and a shoop da woop wannabe; Glutko, an obese gluttonous cyclops; Hectad, a blue wizard guy who melts upon death. Oh and don't get me started on their portrayal of Ganon' a ghost-demon-ogre-pig-bulldog-wizard thing.
The X-Nauts in the second game also engineered the Yux family, floating X-shaped monsters with weird faces that shoot rings of energy from their mouths and spawn "Mini-Yuxes" that will form shields around the main body as long as it's there.
The Pigarithim from Super Paper Mario is a giant piggy bank that shrinks when it takes damage and starts moving faster.
Mount Pajamaja. It's... a sentinent, killer volcano. As in, a volcano with hands, feet and a face that decides it wants to run Mario over in return for Mario waking it up. It also manages to jump off another mountain in pursuit of Mario and co.
Most of the lifeforms in Pikmin are basically this, but the ones that take the cake are a lumpy stone-like thing with what appear to be tribal tattoos that love flowers for decorative purposes, a goldfish on two legs with a natural glass windshield that shoots mortar rounds, a spider merged with a machine that shoots with a machine-gun when agitated enough, and what could be described as a "hominid" made out of water that rolls around on stone rollers and is implied to be an Eldritch Abomination.
In VVVVVV, we have random numbers, buses, glitched-out blocks, lies, and other such enemies. Apparently, all these ideas came from a dream journal the developer kept, which makes them all the weirder.
Many early Resident Evil monsters were necessarily unusual, but they at least looked like products of genetic engineering or bizarre medical experiments. Lately, though, it seems like the design team has just been phoning it in. Sergei Vladimir in Umbrella Chronicles is probably the most relevant example.
Dragon Age: Origins has a fair number of conventional fantasy creatures, but some of the "unique" monsters created for the setting qualify for this trope. At the top of this list are the deepstalkers. Essentially, they're dog-sized, pale-skinned dinosaurs that have lamphrey-like mouths and live underground. They attack in huge packs and can spit acid.
Dragon Age II features the Profane, also referred to as rock wraiths. They appear as floating "skeletons" composed of glowing energy and surrounded by chunks of solid stone.
Albion's wildlife is teeming with strange creatures. The least weird being the Skrinn (carnivorous horned kangaroos), and the Krondir (bipedal lions). Then we get the Varniaks (a cross between a dragonfly and a scorpion), the Rinrii (giant grasshoppers with four eyes) or the Brogg (horned pigs with an arm instead of a tail), and that's not even mentioning the various demons.
Creepers from Minecraft. Most of the other monsters are relatively normal, but creepers are just wrong. It's said that they came about from a failed attempt to make pigs.
There are also Ghasts, giant floating jellyfish-like creatures that spit fireballs.
The monsters added relatively recently continue to be certifiably bizarre:
Blazes are floating heads surrounded by flaming golden rods that orbit them at high speed while shooting fire all over the place.
The Witherking is a massive, flying, desiccated three-headed torso that actually has to be constructed by the player out of skulls and soul sand.
Borderlands 2 has definitely one-upped its predecessor in the weird monster department. Notable are the stalkers, invisible, teleporting creatures that look equal parts bat, scorpion and panther, and the Goliaths, which at first glance are just beefy, helmet-wearing bandits. However, shoot the helmets off and they become enraged, dropping their guns, turning red and coughing up their own skulls, to hang suspended above their shoulders on a rope of viscera as they charge the player fists swinging.
The monsters of Alice: Madness Returns that don't come straight from the books (and naturally even many of those) are utterly bizarre by default: black ooze with mechanical components and broken doll parts sticking out of them, flies made out of iron bolts or ink, predatory fish that live inside ice, wasps in full Samurai gear, crabs that smoke cigars with cannon in place of a claw, doll-heads that fly with four legs attached to them like a propeller that vomit on the played, called 'B—— Babies', etc. etc.
The Classic Mega Man series certainly seems to have their share of these, even though they are robots (the Mets, for example, are essentially living hard hats). The Robot Masters, in particular, tend to be notable in that respect (a robot made out of wood, a robotic centaur, a military camo robot with two heads, a baseball robot (as in, shaped like one), etc). Given that some are made by sane and respected genius inventors, it makes you wonder.
Numerous, numerous enemies in the Parasite Eve series are weird even by JRPG standards. Mostly, in the first game they largely consisted of at least semi-recognizable mutated versions of animals (with exceptions, such as the composite body-part centaur-like creatures in the Hospital) but the sequel took this to new lengths with the ANMC's. Most of those are very animal-like, but with human-like faces and features and studded with visible cybernetic implants. Others, such as Stalkers and Scavengers, one can only guess at the origins. It turns out they were all once human. Including the Stalkers and Scavengers. The 3rd Birthday took that step across the line right into Eldritch Abomination territory with enemies which can only be described as impossible.
While most of the Shades of NieR are basically expies of Heartless from Kingdom Hearts, larger more tentacle-y versions of said Heartless, or monstrous animal-looking things, the giant Shades named Hook (named after the villain Hook from Peter Pan, since all boss shades have some form of fairy tale motif to them) and Wendy are notable exceptions. Hook is basically a hideously lumpy misshapen lizard-thing with numerous breast shaped growths with vague eye-like markings growing under its chin (earning the nickname "chin testicles" by some players), a hand at the end of its tail, and a shark-like head with numerous teeth and Monochromatic Eyes, while Wendy is an Eldritch Abomination made up of a stone sphere surrounded by a swirling mass of pulsating darkness with a great big menacing eye at its center making it look like a closed lotus flower that eats up the local inhabitants of the town, essentially becoming a confused Mind Hive. It's name also makes this a case of Fluffy the Terrible).
Kid Icarus is full of these. Flying eyeballs? Check. Flying noses? Check. One-eyed toad things? Check. Eggplant Wizard? Double check.
Cry of Fear has weird monsters. In fact, they just get weirder as you go along. Chicken-things who's heads explode to stab you with knives, scissor-throwing enemies tied to beds that are floating upside down and female ghosts who's bellies explode, so the fetus can take a stab at you. Literally.
Dofus, a MMORPG... Half the jokes and puns revolved around making bizarro version of common animals and traditional monsters. E.g., the Mopy King is the king of all mop-related monsters... Other examples include the Dragon Pig, the samurai-like Fungi Master, the martial artist known as the Tanukoui-san who needs stilts not to walk on his huge scrotum, strawberry- and mint-flavored jellies, etc..
Kingdom of Loathing is weird, especially for something which has an art style that rarely ventures too far above stick figures. With no context whatsoever, here are some honest descriptions of some of the enemy monsters in this game:
A vined trap-plant with a flower shaped like a stack of steaks in the middle.
A golem made from turkey stuffing and alcohol.
A shapeless blob covered in ears.
The nightmarish, tentacled, pincered Lovecraftian amalgamation of mutated Christmas elves.
The reanimated corpse of a can of asparagus.
The game's co-creator's interdimensional buttocks.
After meeting an owlbear, Vaarsuvius mocks this trope in this strip by postulating the bunnywolf, the ducksnake, and the dreaded penguilion—all of which show up as actual monsters in the first expansion to the OOTS board game.
Pretty much everything that isn't a human in the Whateley Universe story "I Looked into the Abyss and It Winked" since Josie gets dragged into inter-dimensional nightmares and Lovecraft Country. Come to think of it, even some of the humans (like Ecila Mason) are pretty monstrous and freaky. And don't forget Josie's backpack or her so-called 'cat'.
The Elrich setting from The Wanderers Library, and the Library as a whole, thrives on this. Goats that sweat butter and psychic cabbages that serve as royalty are just two examples.
The old Bugs Bunny cartoon with Gossamer, the monster that looks like a giant furry tooth.
That wore tennis shoes!
The Secret Saturdays - The Rakshasa, a giant, purple feline-like cryptid that is able to copy its head and arms on its back to fend off enemies that try to get on top of it..
And then there's Eterno, a thousand year old living mummy whose body is now composed of the salt he was preserved in. He can encase people in this substance by touching them.
Adventure Time is full of monsters that would not be out of place in the furthest corners of a Dungeons & Dragons monster manual. Examples include a Wall of Flesh, a Snake-Armed Ruby Brainbeast, a Crystal Guardian that copies your every action, and an unnamed monster that appears to be 2/3 giant heart and 1/3 electrified skeleton.
A squat, hairy Cephalothorax with blue lips and free-rolling eyes he normally carried in his hands who scared people with his overwhelming stench.
A black and white candy cane with spindly limbs, slit-pupil eyes on eyestalks and big, bloated lips whose primary method of scaring humans was ripping out her guts and showing them to her victims.
The series also revolved around how these three were students learning how to scare humans as part of finding their place in monster society.
Ugly Americans is this taken to an extreme extent, where weird miscellaneous creatures outnumber the "normal" monsters.
The Disgustoids from Secret Mountain Fort Awesome: A purple monster wearing nothing but underwear, a monster made of nothing but butt cheeks, a hairy one with a huge nose, a giant pus ball and blue dog-ish monster.
My Little Pony: Friendship Is Magic loves this trope.While a good deal of the fantastic creatures in the show are from real-life myths(Manticores are from Persia,Hydras,Cerberus and Minotaurs from Greece,Griffins are from Asia and dragons are everywhere)the creators enjoy coming up with their own wacky beasts too.The Parasprites,the Timberwolves,the Ursas(which are living constellations as well) and the Cragadiles are all pretty damn strange.
Wayne Barlowe is an artist who specializes in drawing the weirdest monsters possible.
Cyriak has many weird monsters as well. He animated the 'retarded running horse' above.
The Future Is Wild, as a demonstration of a possible future world, starts getting progressively bizarre as time goes on.
5 million years in the future, nothing too strange has come up yet, although there are the Spinks, birds that look and act like prairie dogs with spade-like front feet, and the Gannetwhales, which are walrus-like seabirds.
Then 100 million years into the future, things start getting strange. The Ocean Glider looks like a giant floating red-and-transparent raft with small sails that is home to groups of defending sea spiders, and the Reefgliders are bulbous creatures with frilly tails. The Lurkfish is a swamp-dwelling electric anglerfish.
200 million years on, and things just start going crazy. The series' Mascot Mook, Flish, are bird-like fish with telescopic jaws. Slickribbons are underground lake-dwellers that are basically giant worms with huge, folding-out jaws. Desert Hoppers are rabbit-sized snails that hop around on one foot. And then there are the squid monkeys and elephant squid, as well as predatory slime mold.
The Platypus is this trope personified, to the point that when it was first discovered, it was thought to be an elaborate sideshow hoax.
Giraffes were thought to be crosses between camels and leopards. They called it a Cameleopard.
Camels, of course, are infamously described as "the animal designed by a committee" for their many different seemingly mismatched parts. Leopards were also considered hybrids back in the day, their name reflects the belief that they were the result of cross breeding between lions (leo) and panthers (pard).
Picture a boar. Blow it up to the size of a shed and remove all the bristly hair. Give it enormous ears and replace its nose with a hollow tentacle with fingers. Yeah, it's amazing that people rarely think of elephants when they think "bizarre animals." Probably because we've interacted with them throughout history and are so used to them.
There is a proverb from somewhere in Africa that goes "When God had created all the animals, he took the leftovers and made the Gnu." The Gnu is better known in the west as the Wildebeest.
The naked mole rat. Hairless, wrinkled, pink as a five-year-old-girl's bike, nearly blind, move as fast backward as they can forward and weirdest of all, are one of only two mammals that are considered eusocial. In fact, the idea of mammals being led by a queen with "drones" is so weird that zoologists still argue about it.
The Cambrian Explosion. You can show people images of these and they will assume they are something from science fiction. But rest assured, they're real. Even the one with 5 eyes and a trunk.
One of them is named "Hallucigenia". I wonder why...
Its name means "unreal". For quite a while, our reconstructions of the creature had it upside-down, and we still don't know which end was the front.
Praya Dubia, the Portrugese Man O' War's deep sea cousin. They live at insane depths, very little is known about them, and the average size is about 130 ft long. For a while, they were on the Eldritch Abomination page.
The goblin shark. In addition to having a long swordfish-like nose, they also have unusual jaw structures. At first, scientists thought that they simply had odd, protruding jaws. Turns out, the truth was even weirder than that, because the jaws of a goblin shark telescope.
Plenty of pterosaurs have this going on too, but the reigning champ among pterosaurs in this department is the Quetzalcoatlus; it was as tall as a giraffe, weighed as much as a grizzly bear, had a wingspan like a small aircraft, took off by essentially pole vaulting and ate baby Tyrannosaurus Rexes for lunch. This video summarizes it perfectly, really.
The assassin spider, with its freaky legs and jaws as long as its neck. Yes... neck. A troper who downright adores spiders might go "what what what is that thing what is going on with its BODY".