One of the great character actors, ever. He went from things like The Patty Duke Show to Wild Wild West and on to Collossus: The Forbin Project (playing Donald Rumsfeld, just 30 years early). I will always remember fondly the recurring character he played on Get Smart, the very ancient "Admiral," or some such title. The character was the doddering old retired director of CONTROL who would fill in for The Chief when he was away from the spy agency. The best running gag was when he'd use a pointer to reach for a map and be just a bit too far way. "Oh Dear" he would mumble, as he surrendered to gravity.
And, except for the obvious heavy makeup of that character, he always looked to be about 50. Even when he was probably 32. what's scary is he still looked 50, last time I saw him. Dorian Grey, your pictures are ready.
I met both William Schallert and Dwayne Hickman in LA about five years ago. In person, you can see they've both had their share of skin "enhancement." Dwayne had a very poor hair dye job, the classic shoe polish look. Both were very nice guys and loved talking about the show.
Schallert was in everything it seems like, since the beginning of television...
Commando Cody - Sky Marshall of the Universe
Mighty Joe Young
Science Fiction Theatre
One Step Beyond
Men Into Space
The Man from Planet X
Tobor The Great
The Incredible Shrinking Man
The Monolith Monsters
And Last, but not least
TOS: The Trouble with Tribbles
and the time travel episode from DS9:
Troubles and Tribble-ations