This video for "Classical Gas" debuted on The Summer Brothers Smothers Show (1968)
From my favorite subreddit, r/ObscureMedia: "Classical Gas - 3000 Years of Art in 3 Minutes." I think I saw some Lascaux cave paintings in there so it really should be "20,000 Years of Art in 3 Minutes."
From Mason Williams YouTube page:
During the time that CLASSICAL GAS was a hit I was also the head writer for THE SMOTHERS BROTHERS COMEDY HOUR on CBS. I had seen a film titled "GOD IS DOG SPELLED BACKWARDS" at The Encore, an off beat movie house in L.A. The film was a collection of approximately 2500 classical works of art, mostly paintings, that flashed by in three minutes. Each image lasted only two film frames, or twelve images a second! At the end of the film the viewer was pronounced "cultural" since they had just covered "3000 years of art in 3 minutes!"
The film was the work of a UCLA film student named Dan McLaughlin. I contacted Dan and told him that I was interested in the idea of using his film as a visual for CLASSICAL GAS to air on THE SMOTHERS BROTHERS COMEDY HOUR. (His original sound track had been Beethoven's 5th Symphony.) THE COMEDY HOUR offered him the money to finance a new film he wanted to make in exchange for the right to change the original soundtrack from Beethoven's 5th Symphony to CLASSICAL GAS and air it on the show. As a music video" it was first shown on THE SUMMER BROTHERS SMOTHERS SHOW (Glen Campbell was the host) in the summer of 1968.