He laid down a pretty good performance a few decades ago in the Andersonville Trial teleplay. Tended to overact, even in early Star Trek, but good, bad, or indifferent, ST was about the only thing going. (I mean, Lost in Space? Now, really!!).
Later on, he became a parody of himself. Some of which, I suspect, is intentional.
Toupee!?? I'd always thought it was his pet hamster!!