Sonic Underground is an animated television series co-produced by DIC Productions, L.P., Les Studios Tex S.A.R.L. and TF1. It is the third Sonic the Hedgehog animated series, and the last to be produced by DIC. It follows a main plot separate from all other Sonic the Hedgehog media, where Sonic has two siblings, Sonia and Manic, that are collectively part of a royal family who were forced to separate from their mother, Queen Aleena, upon Doctor Robotnik's takeover of Mobius due to a prophecy told by the Oracle of Delphius. Along the way, they encounter other resistance groups against Robotnik as well as powerful artifacts that could wreak havoc on the world, all the while searching for their long-lost mother Queen Aleena.

Sonic the Hedgehog is a character created by the Japanese game developers Yuji Naka and Naoto Ohshima. He is the star of the Sonic the Hedgehog franchise and the mascot of the Japanese video game company Sega. Sonic is an anthropomorphic blue hedgehog who can run at supersonic speeds. He races through levels, collecting rings and avoiding obstacles, as he seeks to defeat his archenemy, Doctor Eggman. He is accompanied by supporting characters, such as his sidekick Miles "Tails" Prower, self-proclaimed girlfriend Amy Rose, and friendly rival Knuckles the Echidna.