Sonic the Hedgehog

Sonic the Hedgehog is a blue hedgehog born with the ability to run faster than the speed of sound, and the titular protagonist of the  series. Created to rival Nintendo's Mario, Sonic first appeared in the 1991 title  and has been SEGA's mascot since.

Sonic's journey began when he sought out to rescue the animals of South Island from Dr. Ivo Robotnik's scheme to use them to find the Chaos Emeralds. Since then, sporting a strong sense of justice and a confident attitude, he journeys to preserve peace and protect the innocent, and regularly faces off against adversaries like the evil Dr. Robotnik, now going by "Dr. Eggman". He has fast reflexes and fights by curling into a ball and attacking enemies.

Before Sonic the Hedgehog
Sonic was born on Christmas Island. At some point, Sonic met Dr. Ivo Robotnik, and they have been enemies since.

Donkey Kong Country 2: Diddy's Kong Quest
In the Cranky's Video Game Heroes awards ceremony in Donkey Kong Country 2: Diddy's Kong Quest, Sonic's shoes and Earthworm Jim's plasma gun can be seen next to a trash can, along with a sign saying "No Hopers." This detail was removed for the Game Boy Advance remake, which released after Sega became a third-party.

Mario Kart 8 / Mario Kart 8 Deluxe
In Mario Kart 8 and Mario Kart 8 Deluxe, Sonic's artwork from Mario & Sonic at the Olympic Winter Games is seen on the Mii Racing Suits screen. If the player scans a Sonic amiibo onto the NFC Touchpoint, a racing suit stylized after him becomes accessible, and can be used on the Mii.

Yoshi's Woolly World / Poochy & Yoshi's Woolly World
Sonic's amiibo is also usable in Yoshi's Woolly World and Poochy & Yoshi's Woolly World. The player can scan it to unlock a Yoshi appearance designed after Sonic, sporting blue skin with flesh-colored arms and chest, Sonic's shoes and gloves, and green eyes. Tapping in the amiibo causes Yoshi to instantly take on this appearance, although it can be switched to at the amiibo Hut if it has already been used.

Super Mario Maker
In Super Mario Maker, Sonic appears as a Mystery Mushroom costume, which can be unlocked by clearing 100-Mario Challenge on Expert difficulty or by tapping Sonic's amiibo onto the Wii U GamePad. It can only be used in Super Mario Bros. style. Sonic's sprite is 16-bit, and is based on his sprites from th this makes it the only costume in the game to not be 8-bit. Collecting the Mystery Mushroom giving the player this costume plays the 1-Up tune from the 1991 game Sonic the Hedgehog, and all of Sonic's sound effects are taken from the original games. Pressing Up on the D-Pad causes Sonic to look up while the Ring-collecting sound plays.

Sonic's "course clear" and "lose a life" fanfare are the course clear and game over fanfare, respectively, from Sonic the Hedgehog 3.