I love that little green test-mon, I had to find a way to add it to the Osai Region.

Pluffy, the strange mushroom pokemon
Pluffy is a small grass-type pokemon known from the ghost forests of the Osai Region, though initial sightings of it were from Unova - it may have a wider distribution than is currently recognized. Pluffy have the appearance of small rodent pokemon, though they are in fact plants. They are quite shy and tend only to come out at night, and use a chemical reaction in their body to glow with a ghostly blue light - this may be how they communicate with others of their kind. The spores that they release from their tail have been known to make people see all kinds of crazy things, and because pluffy are so rare themselves, telling someone that they have "spent too long with a pluffy" is basically saying that they're making things up. Pluffy evolves into plufalope with the use of a Shiny Stone.

Plufalope, the strange mushroom pokemon
Plufalope is a small grass-and-fairy type pokemon from the Osai Region, but it is very rare and only a few documented cases of this pokemon existing have been recorded. They are playful and sometimes trick humans for fun by releasing spores from their tails and interacting with the hallucinating person. Sometimes they lead people astray into the wilderness, but they always leave clues for their friends so they can be found before getting into any real danger. In other cases they may encourage the person to sing loudly, to bellow and rage as if trying to frighten off a monster, or to woo an inanimate object as though it were the shrinking subject of their deepest affections. In all cases, the hallucinations wear off with the dawn's light, long after the plufalope has made its escape.