Mouse of Tomorrow. (1942)

How about a Saturday Morning cartoon, y'all?

This is the very first Mighty Mouse cartoon. He was originally called "Super Mouse" in the first several shorts, until Paul Terry found out there was a different Super Mouse in comic books, and changed the animated character's name to avoid confusion. Re-releases of the early 'toons (including this one) had "Super Mouse" dubbed-over with "Mighty Mouse", even though that kinda' screws-up the Supermarket origin joke.

Obviously a parody of Superman, the mouse started out in Kal-El's colors until he swapped-out the blues for yellow in later episodes. Later cartoons gave him different origins, including gobbling vitamins, classical mythology, and a close parallel to Superman's.

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