Sonic Apparition

The Sonic Apparition is a common corruption found in most 2D Sonic the Hedgehog games where Sonic becomes a disembodied head. It is likely a sign the game is significantly corrupted, though can simply be a glitch and not a sign of corruption. It is currently unknown why this is one of the most common corruptions, though some theories say it is the remnant of an unused giant power-up. This however does not explain it's appearance in more than one Sonic the Hedgehog game.

Trivia

 * The Sonic Apparition anomaly is named after the Wario Apparition anomaly found in Super Mario 64 due to their similar appearances as disembodied heads.