When he does the voice of Monkian, his face expression changes to look very monkey-like.
If you listen carefully, you can hear similarities in the voices of the various characters he plays on ThunderCats.
Peter Newman: They (episodes) began running in the Fall and we were still recording when the word came back that it's (ThunderCats) is a hit! It's a hit! I'm sure the thought crossed my mind, 'That means will do more, doesn't it?'"
Peter Newman: I wanted Tygra to be a real guy, a man's man, and so he would help Lion-O develop as a. . . into maturity. So sometimes when I listened to Tygra I said, 'Boy this is a square dude, kinda.'
Peter Newman: We had the freedom to create these characters any way the director would let us, basically, and do whatever sounds and give whatever expression we could. (Talking about ThunderCats.)