A hedgehog chosen by competition
In 1990 SEGA asked its staff to design a character who could take on Nintendo's plumber. The entries included a rabbit that picked things up with its ears, an armadillo, a dog, and a moustachioed man in pyjamas. The winner was Naoto Ohshima's HEDGEHOG, largely because a hedgehog curls into a ball — meaning running and attacking could be the same move.
The colour came straight off the company logo. The red shoes with the white strap were modelled on boots Michael Jackson wore on an album cover, with a red-and-white scheme borrowed from Father Christmas, because the designers wanted something that stood out sharply against green grass. The man in pyjamas was not wasted either: he became EGGMAN.
The rings are a health bar in disguise
Games of that era usually killed you in a single hit. SONIC carries RINGS instead. Get hit while holding any and they burst out across the floor, giving you a frantic second to scoop some back before they blink out. Get hit with none and you lose a life.
It is a small idea with big consequences. It keeps the pace up, because you never have to creep, and it turns a mistake into a scramble rather than a failure screen — which is exactly what a game built on SPEED needs.
Momentum, not jumping
A Sonic level is built around momentum. Slopes turn a run into height, a LOOP only works if you arrive fast enough, and tubes fire you halfway across the ZONE. Where a Mario level asks you to place a jump precisely, a Sonic level asks you to keep moving and trust the hills.
Green Hill, the famous first ZONE, quietly teaches all this. It is wide, forgiving and full of gentle slopes, so a new player discovers on their own that holding one direction builds SPEED, and that SPEED opens up routes along the top of the level that a slow player never sees.
The console war had a mascot
SONIC was a weapon in a genuine commercial fight. SEGA packaged the game with its console, priced it below Nintendo's and ran adverts that named its rival directly — unheard of at the time. For a few years, which machine a child owned was a matter of loyalty, and the BLUE HEDGEHOG was the flag.
The games kept the attitude. Where Nintendo's mascot was cheerful, SONIC tapped his foot impatiently if you left him alone, and the enemies — robot animals called a BADNIK — belonged to a villain who was, transparently, an egg in goggles.
In 2019 the first trailer for a Sonic film revealed a character with small eyes, unsettlingly human teeth and muscular legs. The reaction online was immediate and unanimous.
Rather than brazen it out, the studio delayed the film by three months and rebuilt the character to look like the SONIC people actually knew. It worked — the film did well enough to earn sequels — and it stands as one of the clearest cases of an audience redesigning a character simply by complaining loudly enough.