Okay, we know that Drath take on some sort of twisted form from the host they possessed, but I don't think that this is solely restricted to physical attributes,they also take over a few mental characteristics, too. For example Brody behaves very froglike when he catches that one guy with his tongue, or reminded somewhat of Professor Fike when he started lecturing the people around him (albeit with a sadistic glee). The question is, how much of behaviour like this is mockery of those that have been possessed and how much of this is "unvoluntary"? If a drath would possess a person that is ultra nice, would that make the drath do genuinely nice things, even just for a moment? Might a drath reject someone as a host on the basis that the person is too good?