I always wondered if Steven Hawking was ever actually a guest on The Simpsons or any other cartoon he appears in. Surely he had the easiest voice to fake back before modern robo voices and AI.
He was a Futurama fan and recorded his voice three times for the show. Gygax and Al Gore also did their own voices.
He also did voice work on The Simpsons. In both they sent him the lines and he recorded them at home.
He also did a few live action shows and appeared in Star Trek TNG, The Big Bang Theory, narrated Into the Universe with Stephen Hawking, and hosted Masters of Science Fiction (off screen). He also did some talk shows and some factual stuff, but that's less interesting in this context.
The other places where you see him were people just using a voice synth.
I love both, but what I really love is people doing fun things out of the context in which I know them. That includes both people like Stephen Hawking doing cartoons and people like one of my bartenders on the same Singles Ghost Tour I went on a few years ago (I don't believe but the "history" is fun).