User blog comment:Myself 123/But... The future refused to change/@comment-4220590-20120829162328

Well, the way I see it, the ending of Sonic CD was up to the player. So though the good ending is cannon, I guess that the game designers are allowed to determine how good the ending was gonna be (though I agree it could also be lazyness) and as well allow the future games to decide the true outcome.

Though, if I have to give a justified story guess, I'll say that either Sonic might just have forgotten to fix Stardust Speedway (due to Amy coming after him, hah hah) or that they combined the endings in Sonic CD, so that sonic fixed little planet, but robotnik managed to get one Time Stone, probably the one from Stardust Speedway thus undoing Sonic work there, but then lost the time stone when Sonic threw that stone at him.

Or that it is just an human error and that this is something where we make a bigger fuss about and that little planet is all goof

Still, that is just a theory, but it is fun to come up with. Personally, I like to stick to my second explanation, but I wont invoke fanrage and say that you each has a right to come up with an explanation and then move on, until we get a straight answer.