Because you, the fans, demanded it, Sega is indeed including some of Sonic's pals in Sonic and the Black Knight. Clearly the best part of any Sonic game is the supporting cast. The latest trailer features an epic battle between Sonic and the fan-favorite Blaze the Cat, one of the more complex, multifaceted characters in the Sonic canon. In this game, Blaze plays the part of Percival, one of the Knights of the Round Table. She also fights with Sonic for some reason.
The good news is that once you defeat her in the game's story mode, you can unlock Blaze, so you won't have to play through the whole Sonic game as Sonic. Whew.