Orson Welles' last role was voicing a planet-sized robot
Yes, Citizen Kane Orson Welles. Yes, the Paul Masson Orson Welles. What were the corpulent auteur's thoughts on this final role? He was happy to play a whole planet.

As a side note, I always get somewhat teared-up when Megatron transforms in Galvatron. It's the circle of life, man.