In the PC version, there are several unused animations stored in the game’s files. These include animations carried over from Generations for Classic Sonic, a goal post animation from Generations, a “seek” motion for The Egg Pawns, a damage animation for Silver, early boss fight animations for Metal Sonic, and hand motions for The Golems from Capital City.
Contributed by ShyanVixen
A splash screen for an unused VR mode exists in the files of the PC version.
Contributed by Operationgamer17
SEGA released the Sanic T-shirt as free DLC for the game. The shirt is based on the "Sanic" meme, a poorly drawn MS Paint version of Sonic the Hedgehog.
Contributed by KnowledgeBase