Sprite sheets tell us what was almost there. Dataminers have found unused sprites in the Sonic 1 sheet: a looking-up pose, a different "getting hit" reaction, and even a blinking animation that was never implemented due to hardware limitations.
“Bad.” Tails pulled up a second window. It showed the game—the real world they lived in. Green Hill Zone stretched across the screen, but the horizon was flickering. A palm tree vanished into a block of solid purple. “The corruption is spreading from the sprite sheet into the level geometry. If we don’t rebuild the sheet from scratch, every ‘Sonic’ in every zone will just… stop.” sonic sprite sheet