Aero The Acrobat was no Mario or Sonic, but the mascot had a decent following in the Super Nintendo / Genesis era. Whether you care about the bat or not, the look at the Aero game blueprint is fascinating.
Aero looks nothing like the sketched hero in the sketches seen in the 1992 draft document presented at gaming news site Press The Buttons. These were, indeed, just sketches. They show how one of the many side-scrolling action games that dominated home video gaming in the early 90s took shape. You've got sketches that show off the character's moves, carefully-measured schematics of levels laid out on graph paper, and so on.
Check out the full design document and more about Aero's history at the links below. I never cared much about Aero, but I do enjoy a rare, close look at the birth of a video game.
Aero The Acro-Bat: A Rough Draft Video Game Concept [Press the Buttons]