Based on what we saw in the flashback, it looks like Fluffy is the opposite of everyone else (as in an animal that turned into a human, while the others are humans that turned into animals).
Right, I know that, but what I'm wondering is HOW he got to be a hybrid. We know that some humans started mutating into animal hybrids, but so far there's been no talk of animals mutating into humans.
Based on what we saw in the flashback, it looks like Fluffy is the opposite of everyone else (as in an animal that turned into a human, while the others are humans that turned into animals).