The last of our DC Comics-Filmation shorts from Sesame Street features Superman. As Jughead covered the letter "J", Superman does the same with the letter "S". Here's the clip:
It's been noted that the voice of Superman heard here is that of Len Weinrib, whose voice-over credits include H. R. Pufnstuf, Inch High Private Eye, Doctor Doolittle, and being the original voice of Scrappy-Doo. Clayton "Bud" Collyer, who'd essayed the role of Superman beginning in the Golden Age, passed away in 1969, right before Sesame launched. Weinrib did his best to replicate Collyer's distinctive vocal style for the Man of Steel, enough where fans might've been easily fooled.