Mushroom Hill

Mushroom Hill also known as Mushroom Hill Zone is one of the zones in Sonic Mania and Sonic Mania Plus, but can also be seen in the holiday special; From A. Rose. The area is filled with gigantic mushrooms, topping over a tree's normal height and mostly has orange grass under the person's feet. Some mushrooms even act as springs.

From A. Rose
After Amy Rose finds out that Sonic's rival Metal Sonic is lying on the ground, heavily injured and defeated. Amy decides to bring back the badnik to Robotnik's Lab. She first goes through a part of Angel Island, then onto Mushroom Hill and then onto Ice Cap Zone, before finally arriving at Metal Sonic's home.

Trivia

 * Mushroom Hill Zone does not appear in Sonic Mania or it's extension. It only appears once in this particular holiday special.
 * It is only seen whilst it was snowing on the island, there is no other seasonal version of the zone in this episode.