I had to look that one up! The funny thing is I never actually watched any of these cartoons. It was blatantly obvious that the Evil Mouse was drawn to resemble Newt so I made it a point NOT to watch any episodes. Narf!
The Brain had the looks and voice of Orson Wells (byMaurice laMarche). I do not think it was supposed to be anyone else. My kids, who are grown now, were the right age to watch this when it came out so it was on all the time. I found the adult humor snuck in to be pretty funny.