As a kid I never knew ...
they did a good job with it
I've seen him in other shows naturally bald ...

side note
On Bob Newhart Show Mr Carlin is supposed to be always wearing a toupee BUT in real life he was not bald ... (Hollywood !)

i did not know any of this!!!

Here's a photo of him without his toupee on The Many Loves of Dobie Gillis.

another