Little Planet
From Sonic Retro
Little Planet is a fictional planet which appears only once, in Sonic the Hedgehog CD. It only appears one month out of every year in the skies above Never Lake. This planet hosts the Time Stones, stones which do not grant Sonic any powers, but are coveted by Robotnik. Robotnik chains this planet to a giant rock with a charictichure of his face on it. Eventually Sonic sets this planet free by destroying the rock it is chained to. After flying up for a short distance, the entire planet vanishes.
The US instruction manual adds that the planet is normally covered with tall trees and flowers, however at the start of Sonic CD sand and jagged rocks are featured most prominently.
The JP instruction manual mentions that the planet is also known as Miracle Planet.