I heard a rumor that you have to acquire all 180 Emblems to earn the special stage. I myself am not attempting that kind of feat.
Chat with our AI personalities
unlock him by shagging the boss
In Sonic Adventure 2 Battle(she is very hard 2 unlock get all rank A's with sonic!)Sonic Adventure DX,Sonic Advance 1 2 and 3(in 1 of them you have 2 unlock her).Sonic Riders.
Amy is already unlocked, just choose to play as her
in sonic adventure dx you can only unlock metal sonic by collecting 130 sonic emblems.
Rouge can be played as in... Sonic Adventure 2 Sonic Adventure 2 Battle Sonic Battle sonic riders That is all I can think of.