Sesame Street's original Mah-Nah-Mah-Nah
Oh for the days when kids' TV was made by hippies - most likely under the influence during the script meetings. It wasn't just the UK - it was definitely the case in the US during the early days of Sesame Street.
Check out this classic clip of Mah-Nah-Mah-Nah from Sesame Street in 1969, featuring a beatnik singing freeform jazz with two hippy chicks. TV gold - and to coin a phrase: "They don't make 'em like they used to!"