I decided to scrap this concept, I think it was sorta too out there, especially with the lore. These are Eevee berries, an attempt to make an eevee that grows off of a tree by scientists. They succedded in making the tree produce sentient eevees (that are made of eevee), but the scientists could not figure out how to change the tree's genome so that the eevees that it made would be shaped like eevees and not shaped like fruit, and due to this they could not evovle. So, they just rolled with this and these varities of eevees were kept as house pets that parents grow for their children if they are worriied a normal eevee is too dangerous because the eevee and child might hurt eachother, often called fluffball eevees. Unlike a fruit, Fluffball eevees have the lifespan longer than that of a normal eevee, it is currently unknown why. Just as you would expect from their origin story, they are grown off of trees (their tails function as stems) Fluffball Eevees come in many different breeds, but this project shows the two major ones; circular and oblong.
Added something that @supersonic2752 wanted