Originally planned as the new installment of the Sonic Adventure Series.
Jason Griffith stated in an interview that he suffered from strep throat while recording his lines for the game.
In Japan, the game is actually called "Sonic World Adventure"
The last main series Sonic game to feature Jason Griffith as Sonic, as with all of the other 4Kids! actors, except Mike Pollock, the voice of Doctor Eggman.. But canonically speaking, this was the penultimate game feature Jason, Sonic and the Black Knight was canonically the last.
This is the first game in the Sonic series since Sonic Adventure 2 that doesn't feature Knuckles the Echidna and Shadow the Hedgehog. They were however, originally planned to appear in the game, but were later scrapped.