One of the hallmarks of The Flintstones during its 6 year primetime run (1960-66) was how some celebrities were weaved into storylines. Singer-actress Ann-Margret was one of them, and guest-starred in the episode, "Ann-Margrock Presents". In it, Ann's tour brings her to Bedrock, but, needing to go incognito, she takes a temporary job as a babysitter for the Flintstones' infant daughter, Pebbles. Fred & Barney (Alan Reed & Mel Blanc) join her act while she's in town, this after they catch her rehearsing in Fred's garage.
Here, Ann sings a lullaby for Pebbles. "The Littlest Lamb", for some reason, hasn't been adapted by anyone else for children's records since.