These round little fish live at the bottoms of deep lakes where they walk around looking for food.
Merpeople don't like them much and usually deal with them by tying their legs together, which causes the Plimpies to drift away until they can untie their legs again. But that takes at least a few hours.
(Harry Potter book shout out: In Harry Potter and the Deathly Hallows, Xenophilius Lovegood tells Harry, Ron, and Hermione that Luna is out hunting for freshwater Plimpies when really she's been kidnapped by Death Eaters.)
These demons are small and hairy, but look just like rocks when they crouch down, which is why they enjoy following humans around and trying to eat them.
A Pogrebin will keep following a human, gradually filling them with a sense of despair, until the poor person sinks down to their knees and starts to cries. That's when the Pogrebin will jump on the person and try to eat them.
The best way to get rid of one is by using a hex, using a Stupefying Charm, or just kicking it.
Porlocks live to guard horses. These creatures are only about two feet high and hang out in stables or anywhere else horses are gathering.
They always hide when humans come near. Hey, they like horses, not people.
Puffskeins are little round fluff-ball type creatures who like a good cuddle every now and then.
The weirdest thing about them is that they'll sometimes stick out their tongue and try to eat your snot. It's pretty gross…
…but they make pretty good pets for wizard children.