NCF – Extended list of Neutral creatures.

They aren't the only ones; there are also gremlins! Although, I don't think they were mentioned much in Heroes 6 or 7.

Yes, but there isn't much information about them, and it's not even clear whether they used people as the original material – they're too small, and I haven't come across any specific descriptions.

Added 6 minutes later
It seems like they have some connection with goblins – that is, they are a secondary hybrid.