Thinking about it logically, a godparent/godchild relationship between any two random people is no less weird than in cases in which the couple is famous.
But it seems so. From the wonderful world of Wikipedia comes the fact that Vivian Vance (Ethel Mertz on “I Love Lucy”) was the godmother of The Lovin’ Spoonful’s John Sebastian. Vance and Sebastian’s mother were close friends.
On a non-musical note, the entry says that Vance and her on-screen husband, William Frawley, didn’t like each other. Frawley — who played Fred Mertz –was more than 20 years older than Vance. She once commented that it was silly for him to play her husband. He overheard and never forgave her.
Sebastian has a closer tie to sitcoms, of course: His theme song for “Welcome Back, Kotter” was a big hit.