I managed to get a save just before a cult leader got fully transformed, so I could capture the animation. I already knew they left their skeletons behind (no need for those disgustingly dense human meat hangers!). Not sure if the popping right back up after hunching over and falling to the ground is intended though.
I'm gonna guess it does a death animation, and that the new fishy person that pops up is spawned on the spot (otherwise it would show up as a colonist I guess?)
(Bingo. You can't actually change a gameobject's type.) As for the animation thing, I see why that's happening and will see if my fix works ...
Does the game think that the skeleton left behind is the dead colonist (Mildred Boot in the example above)?
That's the best kind of correct! Not that this would be a priority, but it would probably make sense if after the transformation occurs, the new skeleton person was just deleted entirely.
And, when you say you can't transform, can you add or remove traits/tags for a given object? Or just not completely change it?
I dunno, I quite like the idea that if no one is around to see the transformation that people discover the remains and decide the colonist was killed and mourn their loss.... though this doesn't exactly fit in well with the more recent omnipotent event system that pretty much knows everything about everywhere and clues you and the colonists in so that nothing really happens unobserved.