Unlockable Characters:
Unlock the following characters in Versus mode by performing the corresponding codes:

Play as a Chao – Complete all of Tails’ levels with an A rank
Play as Amy – Complete all of Sonic’s levels with an A rank
Play as Big – Get A ranks on all of Eggman’s Stage
Play as Chaos 0 – Complete all of Rouge’s levels with an A rank
Play as Mecha Sonic – Complete all of Shadow’s levels with an A rank
Play as Tikal – Complete all of Knuckles’ levels with an A rank

With two controllers plugged in and in Sonic’s second stage (Metal Harbour), press Y in the second controller at any time. Sonic will get a board under his shoes and will be able to street board the level with it! However, you can’t complete the stage with this board.

Reuse animals in Chao Garden:

While holding your animal, go as close to your chao as you can without giving it to the chao. Then, just drop the animal in front of your Chao. If done correctly the chao will give the same animation as if you handed the animal to the chao, only you can pick the animal up again. You can also do this with chaos drives.