On the subject of the newer games, the new development staff of Sonic Team admitted in Nintendo Power in a preview feature on Sonic Colors that the were-hog elements of Sonic Unleashed and the swordplay of Sonic and the Black Knight were not good ideas; and based Colors largely around the well-received day stages of the former.
Sonic Team openly despised the early American "Mohawk quill" redesign of Sonic featured in box and promo art, even seeing it as redundant because Sonic was designed to appeal to western audiences in the first place, and only relented when they felt that it and other Americanized changes to the series did help Sonic get off the ground in the long run, and it became a moot point when the redesign was retired in artwork in favor of the original japan design by the mid 90s.
Fan Nickname: Several over the past two decades, but the most recent and most amusing nickname Sonic has been referred is "Generic Sonic", as his current design is referred to in the coding for the Generations demo.
Genius Bonus: Planet Mobius was named for the Möbius strip, a reference to the loop-de-loops founds in the original Sonic game and its sequels. Neat, eh?
Mid Development Genre Shift: The initial concept was a more traditional platformer with puzzles and exploration akin to Super Mario Bros. 2. The final product, while still a platformer, focused more dominantly on its now trademark speed. This evolution is even more prominent in its sequel.
Port Overdosed: The original 1991 game. There is hardly a platform for which Sega has not released a version since going third-party.
What Could Have Been: Sonic went through several character designs before he was settled on as a hedgehog, including a fox, a dog, a rabbit, an armadillo, and a Theodore Roosevelt look-alike in pajamas. Also, his original name was "Mr. Needlemouse" (from a literal translation of the Japanese word for hedgehog, harinezumi). The armadillo idea would later become Mighty the Armadillo, and the rabbit idea is the basis for another Sega game (but with a star instead of a rabbit). Of course, we all know who the Roosevelt man turned out to become. Also, the "Roosevelt" concept was attached to an idea of the hero being some type of "dream warrior" that fought nightmare creatures, likely as a counter to Super Mario Bros. 2. This idea obviously ended up getting reworked over the decade and turned into NiGHTS Into Dreams.
Robotnik's original design was actually intended as the design for the hero, until a change in direction. His concept was actually Theodore Roosevelt in pajamas.
At one point in development, he was much larger and not the main antagonist.
Sonic could have had a human love interest named Madonna.
Sonic the Hedgehog 2 was intended to involve Time Travel with a Good Future and Bad Future possible but the limitations of the Genesis cartridges at the time of development in 1991 prevented this. About Six months later Sonic CD started development with the concepts intact and was released in 1993.
Sonic 3 was intended to have both Tails and Knuckles as playable characters but, after being rushed for time, only Tails was left in the game planning. You can play as Knuckles when the S3 cartridge is locked onto the S&K cartridge, however.
Sonic & Knuckles and Sonic 3 w/ Lock On Technology were intended to be a single large game, code named Project Blue Red in alpha and beta stages, Sega realized that the cost of producing this one game (which would need to be larger then their own self-set system cartridge limits allowed) would out weight the cost of splitting it down and making two games which could be linked together.
Tails was originally planned to be a Tanuki, but this apparently caused confusion due to the Mario franchise already having the Tanooki Suit, so he was made a fox instead.
Both Metal Sonic and his earlier version, Silver Sonic, can be seen in tubes in the Final Egg section of the Mystic Ruins in Sonic Adventure.
Want to know which version of the original Sonic the Hedgehog you're playing? Check out the clouds in Green Hill Zone. In the Japanese versions, they scroll, but in the U.S. versions, they're static.
Also from the original game, there was originally supposed to be a sound test menu with an animated band "playing" the music while Sonic partakes in some breakdancing. It was nixed so the game could meet deadlines, and its space was replaced with the famous "SAY-GUUUUH!" choir heard at the end of Sega's Japanese adverts for the company logo.
Furthermore, the synthesis player of the band, Vector the Crocodile, would go on to become a supporting player in the series.
Yuji Naka reportedly added the seventh emerald and Super Sonic to Sonic 2 as a Shout-Out to Dragon Ball Z. To make it even more obvious, in Sonic 3, Super Sonic had green eyes.
Also introduced in Sonic 2, the Death Egg was a Shout-Out to the Death Star from Star Wars. Supposedly this was to balance out the Japanese fanservice with some American fanservice.
There's an infamous "bug" in the original Sonic Genesis game where, if you land on a group of spikes after being hit without wearing a shield and without landing on the ground first, you will die regardless of the fact that you're supposed to have Mercy Invincibility, at that point. "Bug", because until recently it was thought to be a bug, and not a preprogrammed behavior. Fortunately, all sequels and future releases of the game eliminate this "bug".
Almost all badniks in Sonic CD are based on bugs. The exception is Bigbom, a Giant Mook version of Sonic 1's Bomb badnik.
Sonic characters do not have toes. However, in the cartoons, they do. And if Sonic & All-Stars Racing Transformed is anything to go by, they seem to have toe bones despite not having toes.
Screwed by the Network: ABC put SatAM up against Power Rangers. The results were not pretty. Also, since this was the time when ABC affiliates started airing Saturday Morning Newscasts, some markets never even saw the show first-run.
Word of God: The answers to questions about the series-ending cliffhanger to SatAM were eventually discovered in interviews with the writing staff, including some plot threads which were supposed to continue from this point, such as Snively's Heel-Face Turn, Robotnik becoming Naugus' Right Hand Man as the latter became the series' Big Bad, the introduction of Knuckles, and increased prominence for Tails.