R. White's lemonade: Secret Lemonade Drinker (1973). Ross McManus (Elvis Costello's dad) sang the jingle and Julian Chagrin provided the comic acting, but it's the ad agency that's the real star here.
Allen, Brady and Marsh was a top 5 agency in the UK with a very distinctive approach and a quirky manner of pitching. Other notable campaigns included The Wonder Of Woolies for Woolworth, and Harp Stays Sharp for Harp Lager.
The agency was one of the Jingle Kings of the '70s and '80s, with Secret Lemonade Drinker only rivalled by Do The Shake And Vac by rival agency Benton and Bowles. Both lean into early rock and roll (Lemonade being more Elvis Presley themed).
Both agencies knew that jingles acted as what we now call memes: repeatable, humorous snippets that you can get the audience to spontaneously remember and indeed sing out loud with the right trigger. Mass reach and mass appeal trumps brand narrative or values in this approach, though the latter are carried by the quality of production. The aim is mimetic dominance, with the hope this translates into sales.
Secret Lemonade Drinker was updated and brought back as a campaign in 1992-93 with a mix of celebrities appearing at the end of the ad: John McEnroe, Ronnie Corbett, Mr. Benn. This approach trades on two other popular ad technique: nostalgia and détournement. The audience is assumed to be media literate and steeped in commercial memory, so the agency can play with this.
The jingle is still remembered today in the UK, showing how long lasting exposure to a meme can be. It also mentions the brand name over 20 times in under 30 seconds. Repetition is often the key to successful communication.