In G1, Optimus never really had a mouth (save for when he was Orion Pax). But, the concept of him actually having a mouth that's covered by a face-shield, only when he's in battle, seems to be getting more and more popular, as of late. I know that this concept is used in the new Prime cartoon, the Bay movies (which is arguably the most noteworthy usage of it), Transformers: Cybertron, Animated, and (I think) Beast Wars. My question is: When was this concept first introduced (as far as Optimus is concerned)? Was it in Beast Wars? Or was it in some other thing that I'm not aware of?