Sonia the Hedgehog is a fictional character created for the animated television series, Sonic Underground, which takes place in an alternate universe. She is an eggplant-colored anthropomorphic hedgehog with orchid spikes and hair of the same color. She bears a close resemblance to the Sonic CD design of Amy Rose. In this universe, she is the sister of Sonic and Manic the Hedgehogs, as well as the daughter of Queen Aleena. Unlike her brothers, she does not have tan colored arms and stomach/chest. In regard to wardrobe, Sonia wears a dress with a short dark purple skirt, and a red sleeveless top. The two sections are separated by a gold belt that forms a pointed shape at the front with a small circle in the center of the belt. Unlike most Sonic characters who wear gloves, hers are purple and go up to the elbows rather than the stereotypical white hand gloves. Sonia also wears red stockings under dark purple boots, the toes of which are a matching red.
Like her brothers, Sonia's speaking voice is done by Jaleel White, but her singing voice is done by Stevie Louise Vallance.
In an alternate reality Sonia is a member of The Royal Corrupts Hedgehogs with alternate Sonic and Manic and is a fashion obsessed who only thinks in her beauty.