Sonic the Hedgehog different media including animation, comic books, and a Hollywood film. The first "Sonic" game, "Sonic the Hedgehog", is a platform game released in 1991. Players control the anthropomorphic blue hedgehog Sonic, who can run and jump at high speeds using springs, ramps, and loops. Sonic must stop Dr. Robotnik from taking over the world using the Chaos Emeralds. "Sonic the Hedgehog 2" (1992) increased the overall size and speed of the series' gameplay and was the second best-selling Genesis game. It introduced Sonic's sidekick and best friend, Miles "Tails" Prower, who followed Sonic throughout the game, and allowed a second
Sonic the Hedgehog 2 was released in 1994, two years after "Sonic 2". The "Sonic & Knuckles" game cartridge features a special "lock-on" port into which the player can insert other Genesis cartridges. Attaching "Sonic 2" unlocks "Knuckles the Echidna in Sonic the Hedgehog 2", a variation of "Sonic 2" whereby the player plays as Knuckles the Echidna, a character introduced in "Sonic the Hedgehog 3" and not playable until "Sonic & Knuckles". Though the game is largely identical to "Sonic the Hedgehog 2", Knuckles is able to glide and climb walls, allowing him access to areas previously inaccessible to Sonic or Tails. However,