Board Thread:Questions and Answers/@comment-27511601-20161028210536/@comment-477304-20161029092611

KillRoy231 wrote: If you mean traveling from planet to planet, then when he was on Little Planet after Sonic CD, got revived by Eggman through a drone, and flew to Earth in Sonic the Hedgehog 4 Episode II (in the section Episode Metal)

He's also been to Planet Mobius in Sonic Triple Trouble Mobius is non-canon. That was just the westen manual that mentioned Mobius and it did so in that context that it is Sonic's World and always has been. It's also important to point out that AoStH's Robotnik design is on the box art, but not used in the game. These things were used to loosely tie into the show. Nothing more.