Nuclear Nasty

A sub-trope of I Love Nuclear Power, Nuclear Nasty is a monster (usually the Monster of the Week) created when a creature is exposed to radiation. Very common in 1950s monster movies, as well as works trying to be throwbacks to that era for obvious reasons. Tends to be an Attack of the 50 Foot Whatever.

When played straight, this is a case of You Fail Biology Forever.

Anime

 * Kimba the White Lion has a grasshopper becoming a huge one thanks to a nuclear mutation.

Comics

 * There were quite a few radiation created monsters in Marvel's early monster comics, including a fairly adorable weed with mind-control powers and a scarecrow of all things made giant and mobile by nuclear radiation.
 * The French comic Les eaux de Mortelune (The waters of Deadmoon) had mutant animals. Lyon is now inhabited by giant flies, Avignon by giant termites and Les-Baux-de-Provence by giant telepathic praying mantis.

Film

 * Them is probably one of the most well known movies featuring this trope.
 * Godzilla may well be the mascot for this trope.
 * The mutated algae in The Horror of Party Beach possess human corpses, which, for some reason, tended to look in practice like a muppet of the Creature From the Black Lagoon with a mouth full of hot dogs.
 * Bert I. Gordon loved this, whether it's the giant grasshoppers from Beginning of the End, The Amazing Colossal Man, The Food of the Gods, the horrible cyclopic giant from The Cyclops, or the giant ants who mind control people by farting pheromones on them from Empire of the Ants.
 * Roger Corman also had quite a few of them, like The Beast who Brings Death With Its Touch from Teenage Caveman, the three-eyed; horned; big-nosed mutant from The Day The World Ended, the giant leeches from Attack Of The Giant Leeches, and the titular creatures from Attack of the Crab Monsters.
 * The Incredible Melting Man, with an incredibly disgusting appearance done by Rick Baker himself, who gets stronger as he melts (How that works is anyone's guess).
 * The movie started off as a parody, but the distributors wanted it to be a serious horror film and exorcised all of the comedy from the final cut.
 * The B-movie From Hell It Came featured a tree-man named Tabonga. Head Injury Theater article here.
 * Tromie, the giant, mutant radioactive squirrel from the not-quite-serious Class of Nuke Em High series by Troma.
 * Last Days of Planet Earth a.k.a. Prophecies of Nostradamus features a few creatures mutated by radiation in New Guinea. Carnivorous Trees, poisonous leeches, flesh eating flying foxes (big ol' bats), and cancer-ridden human cannibals. That last one got it banned in Japan--where it was made.
 * The Beast of Yucca Flats has a man getting caught inside a nuclear test explosion, becoming the eponymous beast.
 * CHUD had homeless people in New York's sewers turned into mutant cannibals by illegally dumped radioactive waste.
 * The original Night of the Living Dead includes a speculative Hand Wave about radiation from a returning space probe to Venus causing the Zombie Apocalypse. This explanation is discarded in the subsequent Dead films, however.

Literature

 * Andre Norton's Star Man's Son had mutant creatures in a post-apocalyptic world.
 * Metro 2033. Looks like the heavily irradiated, post-nuclear Moscow became a gigantic nest of monsters, mutants and dinosaurs.

Live Action TV

 * The X Files: Fluke man!

Tabletop Games

 * All over the place in Gamma World, though modern versions use Nanomachines and Magical Particle Accelerator as an explanation. Some of these include giant insects, the many-legged Centisteed, the multi-armed Snake People called the Menarls, the Exactly What It Says On the Tin cactus horse, the humanoid metal-to-rubber-making bunny rabbits called Hoops and The Yexil.
 * Monsterpocalypse has those cosy radioactive giant insects that eat you, instead of making you a super hero.
 * Although it was mainly based on hard science, the After the End game The Morrow Project allowed for radiation-mutated animals that were treated as monsters.
 * Mutant Future had mutated monsters.
 * Paranoia had at least one mutated monster: giant intelligent cockroaches in the adventure "Into the Outdoors with Gun and Camera".
 * D 20 Modern's Urban Arcana setting has the Nuclear Toxyderm, a pile of nuclear power plant waste given life.
 * Promethean: The Created has the Zeka, nuclear Prometheans who have the ultimate in Blessed With Suck. Not only do they suffer Disquiet, they spread fallout wherever they go, meaning they can rarely interact with humans and have a lot of trouble undertaking the Pilgrimage. As a result, most of them go Centimanus, and hoo boy, do they go Centimanus. Two NPC examples are Oleg Wormwood (an Eastern European arms dealer who longs to get his hands on a suitcase nuke and start some real fun) and Tsar Bomba (a hulking brute who seems content to just barge into nuclear power plants, subject the staff to a slow death, and bask in the radiation as the place starts to go critical). And that's not even starting on the Carcinomas...
 * Zeka can have a Bestowment (innate power) that lets them irradiate corpses to bring them back as zombies. The Irradiation tree of powers also includes the abilities to control insects and then, later on, to mutate those insects into giants (ala Them). It's also mentioned that the Wastelands created by Zeka tend to include huge, mutated invertebrate lifeforms.

Video Games

 * Being inspired in part by 1950s sci-fi and taking place after a nuclear war, the Fallout series has a bunch of these. Mutated animals include roaches, mantises, scorpions, flies, ants, geckos, rats (including Mole Rats larger than an adult human), bears, cows and Tarantula Hawk Wasps.
 * The tarantula hawk wasps were actually genetically engineered by a Mad Scientist. You get to meet him in Old World Blues.
 * Used seriously, but knowingly, in Metal Gear Solid 3 to explain why some of the animals are bigger (like the tree frogs) or more aggressive (like the gavials) than they are in real life. Para-Medic even compares it to Godzilla.

Real Life

 * There has been investigation into whether nuclear accidents like the Chernobyl disaster have mutated animals over generations. It didn't.
 * In Real Life, this wouldn't be able to happen. The nuclear poisoning will kill any higher animal or at least give health problems. The childs of given animals may have some abnormalities but usually not good.