The Flintstone Canaries
Cartoon character Fred Flintstone puts together this barbershop quartet in "The Flintstone Canaries" episode (10/24/1964) of animated television series The Flintstones. Fred forms the group to win a contest on the Hum Along With Herman TV show (a parody of Mitch Miller's TV show, Sing Along with Mitch), but they can't sing.
They find Fred's pal Barney turns out to be a natural tenor- but only when he's in the bath. They get him to join the group and the group ends up on the show singing in a bathtub- not for the contest, but for the show's sponsor's, Softsoap.