In my head Woody Boyd and not Gary Portnoy sings the “Cheers” theme.
Lawrence Hilton-Jacobs, the actor who played Freddie “Boom-Boom” Washington on Welcome Back, Kotter, was often asked if he sang the theme song. It was actually sung by John Sebastian. Hilton-Jacobs once sang it on a talk show, mainly to prove that he sounded nothing like Sebastian.
Of course David Cassidy sang the theme from the Partidge Family. I can’t possibly imagine any studio singer doing it.
I really can’t. Honest.