Sonic X - Season 2 (2004)

When Dr. Eggman learns that Knuckles has just discovered the oldest map in the world, which holds the location of the lost continent of Murasia, he sends Decoe and Bocoe on a mission to take the map away from Knuckles.

Sonic and his friends are in pursuit of Dr. Eggman who has fled into the volcano which lies at the world's bellybutton. They come upon the Murasians ruin which attributed its destruction to a supposed dragon god.

Dr. Bickley discovers that Sonic's world and theirs were once one and the same. As the two world slowly completes its reunification, she realizes that the process would ultimately cause time to stop. The only solution? Send Sonic and the rest back home.