Michael Sporn had the great luck of breaking into the animation industry at John and Faith Hubley’s studio, Storyboard, in the early-1970s. He’s posted some fascinating remembrances on his blog about his time working on the Hubleys’ LETTERMAN interstitials, produced for PBS’s THE ELECTRIC COMPANY. Read them HERE.
It’s also worth noting that last month a 4-disc dvd collection of THE ELECTRIC COMPANY was released. Not sure how much LETTERMAN is on it, but surely, there’s at least a few episodes.