Each game focuses on the titular protagonist Sonic the Hedgehog, an anthropomorphic blue hedgehog. Eggman/Robotnik from Sonic the Hedgehog. A character named Hedgehog/Porcupine is a mentor to Stalker. Sonic the Hedgehog is a video game series. Suspicious, Sonic the Hedgehog and his best friend Tails investigate. They are led by Sonic the Hedgehog and Princess Sally Acorn, the King's sole heir. A gradient of BMP signaling is found in opposition to a Sonic hedgehog, Shh, gradient. Eggman revives the antihero Shadow the Hedgehog from dormancy. Licensed characters like Sonic the Hedgehog and Mega Man are not included in this list. "Sonic CD" is a side-scrolling platform game similar to the original "Sonic the Hedgehog". The Japanese began work on "Sonic the Hedgehog 3". The game's premise is similar to that of the original "Sonic the Hedgehog". "Adventures of Sonic the Hedgehog" received mixed retrospective reviews. He first appeared in the 2006 "Sonic the Hedgehog". Jun Senoue is well known for composing music for "Sonic the Hedgehog".