In the final season of The Flintstones, the show's writers began skewering pop music more so than in previous seasons. In fact, it was in the season opener that Pebbles & Bamm-Bamm became pop stars in a dream that Fred (Alan Reed) was having. Shindig host Jimmy O'Neill crossed over, along with the Beau Brummels, for one episode.
In the episode, "Masquerade Party", a quartet of aliens land in Bedrock, and their unique look enables a record company executive (Mel Blanc, using his Secret Squirrel voice) to dismiss the Beasties (Beatles parody) and sign a group now known as the Wayouts.
Reed is also heard as Sam Sandstone, a fellow member of the Water Buffalo lodge, who sounds suspiciously like Fred.
It just so happened that Secret Squirrel debuted that same year, albeit over on NBC, which would pick up rerun rights to The Flintstones not long after the series ended.