There was a time when Sesame Street's classic animation sequences were hard to find, and when finding the details of their creation were even harder. In the early days, Daddy Types spent an inordinate amount of the kid's naptime researching this stuff, and making the info more widely available.
One of the by-products of this effort, and the broader increase in our cultural knowledge, is that we know to mourn the passing of Jeff Hale, whose animation studio Imagination, Inc. made so many of the OG Sesame Street animations of the early 1970s.
Hale was 92, and he will be missed. Fortunately, Imagination, Inc.'s wonderful creations like Pinball Number Count, Jazzy Spies, Capital I, 4-Armed Swami, and many more, will live on, at least in low-res glory, as a studio fire at Imagination, Inc. destroyed most of the original material long ago. [Actually, the compilation above is pretty clean. I'm watching now.]