I had no idea this is how the Seinfeld theme was made. From the custom keyboard sounds, both with bass and mouth sounds, to the playing along with the intro differently depending on the cadence of each joke. I guess I have to rewatch Seinfeld again now!
Bonus points in my mind go to Forgetting Sarah Marshall because Peter (Jason Segel) plays a Seinfeldian bass line on keyboard at his crime show composing job, then uses a music stand to destroy a projector screen in vengeful anger. I now recognize this a clear reference to how the theme was composed, just another layer in how great that movie is!