* AbsenteeActor: ''Black Knight'' is one of four games in the franchise where Dr. Eggman is completely absent, the others being the three Tails spinoff games.
* FranchiseKiller: ''Black Knight''[='=]s poor critical reception and commercial failure seems to have killed off this series of spinoffs.
* WhatCouldHaveBeen: ''Secret Rings'' began life as a Wii port of ''VideoGame/SonicTheHedgehog2006'', with the developers experimenting on playing the game largely with motion control. Development then switched to making an all-new ''Sonic'' title exclusively for the Wii, designed to take full advantage of the hardware, and thus ''Secret Rings'' was born.
* WorkingTitle: ''Sonic and the Secret Rings'' used to be ''Sonic Wildfire''.
** For a short while between ''Wildfire'' and ''Secret Rings'', it was also going to be called ''Sonic and the Secret of the Rings'', but they took out the "of the" to make it a bit less wordy.