More often than not, monsters are created accidentally -- thank you so much for all-powerful mutant Piers Morgan, CNN -- but sometimes they're deliberately unleashed, by, say, the happy couple behind Stitches & Glue. This pair of purchasable-creature creators "met across a workshop table whilst making a 10ft ogre puppet", and have since teamed up on shoots like the last X-Men and Tim Burton's upcoming Dark Shadows (a gothic fantasy starring Depp and Bonham Carter?? Now we've seen everything!).
They specialize in custom jobs, and'll Frankenstein you a huge variety of furry beasts -- from 2ft-high, ape-like bipeds w/ pose-able limbs, crooked sticks & monocles, to a tree-loving "Oak" monster w/ miniature antlers -- all of which'll come with their own "unique name and story", because at a certain point, even they get tired of cutting and pasting.
They do semi-mass-produce some terrors, like a fireside Monster Rug designed to look like a bearskin with gnarlier claws, as well as keyring-friendly Lucky Monster Paws that also come in a larger, "luxurious" variety with a "royal purple" hue, so clearly they're still just as Harry.
Proving they're not monsters themselves, they're even providing "freebie" fiends (incl. the three-eyed Paper Monster & the Siamese Monster) that you can literally print out and fold up right now, so easy it's almost taking the Pi...ers.