A recent episode of Big Bang Theory features Sheldon playing Words
with Friends against Stephen Hawking (thus concluding that he must be
“friends” with Stephen Hawking).
At the end of the episode, Stephen Hawking calls Sheldon, berating
Sheldon for losing. However, we never actually *see* Dr Hawking.
The credits, however, mention Dr Hawking as a special guest star. This
is normal when a celebrity voice appears in a TV show (even if the
celebrity himself does not appear), but seems a bit odd here, since Dr
Hawking’s voice is computerized text-to-speech.
It’s possible that Dr Hawking uses a special text-to-speech program
that isn’t available elsewhere, so it really is “his” voice on the
show. It’s also possible the producers just wanted to credit Dr
Hawking, who has appeared in person on the show previously.