Sonic the Hedgehog protagonist Sonic the Hedgehog, a blue hedgehog able to run at supersonic speeds, and recurring villain Dr. Eggman, an evil scientist whose ambition is to conquer the world. Among Sonic's many allies, the most well-known include: Miles "Tails" Prower, a twin-tailed, highly intelligent yellow fox who is Sonic's sidekick and best friend; Amy Rose, a pink hedgehog who is Sonic's self-proclaimed girlfriend and a hero in her own right; Knuckles the Echidna, a coolheaded red echidna who is the guardian of the Master Emerald; Shadow the Hedgehog, an anti-heroic doppelgänger of Sonic with a dark past; and Metal Sonic, a
Sonic the Hedgehog elements from the cartoons "Sonic the Hedgehog" and "Adventures of Sonic the Hedgehog". "Dr. Robotnik's Mean Bean Machine" was a puzzle game similar to "Puyo Puyo" that was set in the "Adventures of Sonic the Hedgehog" universe. "Sonic 3D Blast", an isometric, 2.5D platform game released in 1996 and developed by Traveller's Tales, featured Sonic running through pseudo-3D environments while trying to rescue Flickies from Doctor Robotnik. The Sega Genesis had "add-on" systems that incorporated "Sonic" games. "Sonic CD", released for the Sega CD, was a 2D platform game released in 1993. The game introduced the characters Amy Rose and