Conforme explicado no Reddit :
Sha na na was a "faux retro" group that sang doo wop songs from the 50's (which is why Abe liked them). Bowzer was a popular member of the group (the joke in the show was a goof, however, because Bowzer didn't join the group until after their Woodstock performance in 1969).
Jon "Bowzer" Bauman, conforme descrito na Wikipedia :
Jon "Bowzer" Bauman (born September 14, 1947) is an American musician, best known as a member of the band Sha Na Na, and game show host. Bauman's popular Sha Na Na character, "Bowzer", was a gangly, slender-armed greaser in a muscle shirt.