I went in for a meeting with Matt Groening and he played me a pencil sketch of the opening to "The Simpsons". It was a little reminiscent of "The Flintstones" as they also flipped around in a car, though they were running it with their feet, still had that crazy energy.

I wrote it in my head in the car on the way home, ran down to my studio and made the demo and then sent it in on cassette the next day. I shortly got the message "Approved. Ready to go."

It's pretty clear to me at this point, even though it only took 1 day of my life to do, that if I were to die today, right now, that it would read "Danny Elfman (1953-2017) He wrote "The Simpsons" theme. D'oh!"

http://ew.com/tv/2017/11/15/justice-league-danny-elfman-composer-interview/