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 (character) on this basic attack and two of these enhancements have become mainstays of his: the Spin Dash which was introduced in "Sonic the Hedgehog 2" and involves Sonic spinning on the spot before blasting off at full speed, and the Homing Attack, officially introduced in "Sonic Adventure", in which Sonic dashes toward a target in midair. Sonic's only weakness is that he cannot swim, sinking like a rock if plunged to a deep body of water. The only exception is that he can swim in the Sonic the Hedgehog Adventure Gamebooks. When the seven Chaos Emeralds are collected and used,