Little Planet (In Another Time, In Another Place)

The Little Planet is an alternate version of the same planet from the Another Time, Another Place reality. At one point in the past, Sonic the Hedgehog ventured around the planet to rescue Amy Rose, where he battled and defeated Metal Sonic. (SSSM: #3)

Much later, the planet was once again about to pass over Sonic's world. Doctor Eggman took advantage of its return by heading there to retrieve and revive the damaged Metal Sonic. (SSSM: #3)