[he actually spent some time thinking about this and theorizing. He looks pleased to be sharing his thoughts out loud with someone. It's the sort of thing he would've done with Igor, and because of this he slips more into science mode]

That's a difficult question to answer. I didn't interact long with the first one I brought back and I didn't even know the second. I can't really reach a definite conclusion on changes to their personality, but since they exhibited similar behavior, I can conclude it wasn't all part of who they were before.