Monster Mash
A massive crossover between iconic monster from popular culture.
Most commonly found in a setting where the heroes live in a world where this creatures existed and may be part of a Crossover Cosmology, especially if they themselves are supernatural. The creatures, rather than becoming shut-ins who never leave their designated niche or dark corner of the world... they actually socialize. Vampires and werewolves, usually antagonists, agree to keep up a mutual hidden existence against humans. Fairies and ghosts work together to scare local homeowners. And the wizards work with all of them to save both worlds.
Is not really necesary it had to involve terror of any type.
Examples:
The Monster Squad: The movie has Count Dracula attempting to raise an army of darkness with the assistance of Frankenstein's Monster, a werewolf, a mummy, and a gill-man.
Goosebumps (2015): The movie and it's sequel had monsters from the titular books that they were releashed.
Hotel Transylvania: The main characters are Dracula and his daughter; their friends and guests include a mummy, a werewolf, Frankenstein, witches, an invisible man, a blob, and more. Justified by the title setting being, well, a hotel for monsters.
Nightmare Before Christmas: The citizens of Halloween Town include living skeletons, ghosts, zombies, witches, vampires, a werewolf, a devil, a monster clown and a mad scientist with his stitched-together creation, along with many original monsters.
Monsters vs Aliens (2009): The movie includes versions of the Fifty-Foot Woman, the Fly, the Blob, the Creature from the Black Lagoon, and Mothra are gathered together to kick alien butts. The Invisible Man also used to be a member of the team.
Castlevania: This video game saga, practically runs on this trope, with demons and mythical monsters thrown in for extra variety. Hell, even Cthulhu makes an apperance, as does Leatherface in Order of Ecclesia.
One Piece: The Thriller Bark Arc has a mansion filled with Zombies that do double duty as frankenstein's monsters, an invisible man, a ghost girl who controls ghosts instead of being one, an invisible mix and match critter, a mad scientist, and their leader who bears a striking resemblance to a vampire and has a special ability that renders its targets unable to touch sunlight without burning up.
Ed, Edd n Eddy's Boo Haw Haw: Ed, after watching too many horror movies, hallucinates seeing the cul-de-sac kids as monsters of a different varienty, as witches, aliens, vampiresses, gorgons, a spider monster, etc.
