Ohoo, that's pretty cool! [As he stood up he put a hand to his chin, starting to idly pace around in thought.]

I wonder if there's any way around here to test for sure. [Facing Donnie he tilted his head slightly, scrutinizing him.] I could certainly see the terrapin. I'd have to know more about your brothers to be able to guess more...

[He was looking pretty eager now.] This could be a whole new thing to look into! Discovering your original species, pre-mutated DNA.