I think it's kind of based on the Kenner action figure look. (Kenner versions of some cantina aliens and vehicles keep popping up.) And if you recall, TCW was initially criticized for it's characters looking like marionettes. Which was ironic, since Lucas said somewhere that Thunderbirds was a design influence.

I can't think of any modern shows in that age bracket that so casually kill off the bad guys, if at all. We've come a long way from the days of G.I. Joe. ;)

And Frank Oz is probably the only person on the planet who can go off script with Yoda.