Psychologically, the closest human profile you could find, is this of the "hoarder". www.youtube.com/watch?v=MYBsPv…
A mushroom's life is spent on expanding and nothing else. Living with metal scrappers have had the double effect of making this creature extremely brutal and cunning, and making it prone to seek and hoard as much bits of metal as it can, and even fusing with metal.

Mushrooms are usually flaccid, sluggish beings. And bones are the only thing about mammals' anatomy that they can't seem to replicate. But living with scrappers, who spend their lives doing everything with metal, gave the Recycler an easy way around this natural tendency.
The Recycler is an ugly mushroom. Lived for years among other metal scrappers in the inner city wasteland, some would say for too long. Mushrooms have this tremendous ability for mimicry. Whatever their environment is, assuming it's moist enough for them to prosper, they evolve to adapt to it as perfectly as one could hope to; they BECOME this environment.

He ended up building a metallic skeleton for itself, or rather, an elaborate frame made of mobile pieces, allowing it to shapeshift and keep growing with time; not to mention giving it a literal iron grip. It would take it a good hour and a half to get the skeleton inside its body, assembled and functioning. Its aspect is gross. It just doesn't need to replicate an overly attractive body. But would it need or just want to, maybe it could.

They say its body evolved to digest mammals meat and it eats its enemies and random people it comes across. Not sure if that counts as cannibalism. Well, it couldn't just get such a trait out of the blue now, could it? mushrooms usually feed on... whatever mushrooms feed on. My guess is that it eating dogs is merely the result of living in an environment where dogs eat dogs. Know what I mean?