This song was on the Flintstones in the 60s. In a dream, Fred imagined that Pebbles and Bam-Bam were infant musical prodigies who became world-famous singing that very song. Let The Sunshine In. Fred was their manager or some other ridiculous crud.

This was during a very dismal period in American TV where shows began to realize that they could make a lot of money with a hit single, especially if the singers had hair like the BEATLES.