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Sonic - Did You Know Gaming? Feat. WeeklyTubeShow
 
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There's an unused sprite found in the game of a bloody skull with Japanese text the reads "tobu" (とぶ), which means "to fly, to jump". There is no evidence to indicate what it was meant for, it is quite possibly a joke.
Contributed by Cupleaños
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Mighty the Armadillo's sprite sheet is nearly identical to Sonic's sprite sheet from Sonic Crackers, a Genesis prototype game from which Knuckles Chaotix drew its elastic ring mechanic.

This has led fans to speculate that Sonic was originally intended to be in the game instead of Mighty, but was changed late in development. This, as well as the theory that Tails was also meant to be included, is backed up by other assets in the game, including Amy Rose being hidden in a sound test and Sonic and Tails appearing in the ending screen when the game is completed with all 7 Chaos Rings.
Contributed by MidwayCJ
Knuckles Chaotix is the only Sonic-related game released on the Sega 32X.
Contributed by davidcon
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Standing still for a minute will cause Metal Sonic to appear and attack.
Contributed by DidYouKnowGaming