Greg responds...

That developed naturally over Coyote's many appearances. Bronx so effectively chewed up half of Xanatos' face in "Leader of the Pack" that we maintained that head in "Upgrade" at which point it became symbolic of Coyote, and was used as a visual tie-in in "Grief" and "Cloud Fathers".

As for who came up with the notion of a humanoid robot with half its face destroyed. Well, we certainly weren't the first, but neither was the Animated Batman. The earliest I can think of off the top of my head is the original Star Trek, but I'm sure that bit goes even further back.