…or did the perm thing just “happen” with no explanation?
It was the 70’s.
And his boyfriend probably helped, too.
Or as his short hair grew out, it became curlier, which I assume is the explanation for the rest of the men in the family going from straight to curly. (A lot of guys with curly/wavy hair keep it super short so they don’t have to mess with “styling” it.)
It was the 70s, as beajerry said.
Do most shows feel the need to explain new hairstyles on their characters?
There was no on-air explanation and as has been stated, during the 70’ it was quite acceptable for men to suddenly appear with perms.
Yeah, the one I really want to see xplained was Corporal Newkirk on Hogan’s Heroes with his '60s Beatles style 'do in the show which took place in the '40s 
In the 1980’s TV series “Day by Day,” the son had a dream that he was one of the Brady Bunch. The actual Brady Bunch actors participated in the dream sequence, including a pregnant Marsha and the Brady men with their perms. Mike explained the perms kept their hair out of their eyes when they fixed their bikes.
See http://us.imdb.com/title/tt0094446/
I won’t ask you why you want to know if you won’t ask me why I know the answer.
snafiasco – welcome to the boards. Judging by this answer, you are definitely one of us.