Sonic the Hedgehog (ソニック・ザ・ヘッジホッグ Sonikku za Hejjihoggu) is a video game franchise created and owned by Sega. The franchise centers on a series of speed-based platform games, but several are spin-offs in different genres. The protagonist of the series is an anthropomorphic blue hedgehog named Sonic, whose peaceful life is often interrupted by the series's main antagonist, Doctor Eggman. Typically, Sonic—usually along with some of his friends, such as Tails, Amy, and Knuckles—must stop Eggman and foil any plans of world domination. The first game in the series, published in 1991, was conceived by Sega's Sonic Team division after Sega requested a mascot character; the title was a success and spawned sequels, and transformed Sega into a leading video game company during the 16-bit era in the early to mid-1990s.
Sonic Team has since developed many titles in the franchise. Prominent members of its initial staff included Naka, character designer Naoto Ohshima, and level designer Hirokazu Yasuhara. Other developers of Sonic games have included Japanese Dimps, American Sega Technical Institute, Backbone Entertainment, Big Red Button Entertainment, and Sanzaru Games, Canadian BioWare, and British Sumo Digital and Traveller's Tales. While the first games in the series were side-scrolling platform games, the series has expanded into other genres such as action-adventure, fighting, racing, role-playing, and sports. The series has sold 150 million units as of November 2014, making it one of the best-selling video game franchises of all time.