Now’s my chance! Here are some of my favourite old Sonic headcanons/hills I will die on:
Sonic and Silver were both the result of research from Project Shadow, but they were not Intended Use of The Technology.
Gerald set up Sonic’s creation chamber before GUN caught him, and programmed it with a time delay. Sonic is the one he’s referring to in his diary entry talking about ‘I will leave everything to him / release and awaken it to the world’. However, something went wrong and Sonic was let out early: before he was done growing and, critically, before Gerald’s mental programming took effect.
(Gerald thought the original Shadow was dead at the time and intended to name Sonic after him)
(I legitimately think this was a reveal SEGA was building up to that they chickened out of)
Meanwhile, in the bad future, someone discovered Sonic’s old chamber and managed to get it working with some modifications to the end result, which is where Silver came from.
Yes this does mean that Shadow, Sonic, and Silver are all technically brothers, and some of the knock-on effects that implies like them all being ageless.
A lot of Shadow’s in-universe design was based on Gerald’s research on Angel Island, specifically the mural of Super Sonic fighting Eggman’s mech for the Master Emerald from Sonic 3 & Knuckles.
We know Gerald was there at some point because the Eclipse Cannon’s core was based on the Master Emerald shrine from Sonic Adventure.
Shadow has the following qualities in common with Super Sonic: is a hedgehog, has red eyes, his spike configuration, his golden aura (at least in SA2, don’t know offhand if that’s been kept up - the little flash he gets when he spinjumps is gold), and flight (via the jet boots - it’s why he has them!).
Shadow was treated perfectly reasonably on the ARK, kind of like a gifted child, and that’s why he didn’t go into depressed angry bioweapon mode until after the shutdown.
He was very much not treated reasonably when GUN first captured him after the shutdown. Whether or not he retains/recovered those memories is up in the air.
Knuckles really is the last echidna because the Master Emerald created him. It needed a guardian and its previous guardian was too off the rails, so instead of a Chao-based one it created a Mobian-based one with the only template it had available: Tikal.
Mobians and Chao have a relationship similar to humans and chimpanzees: Chao are Mobians’ closest living cousins, evolutionarily, which explains a lot about Mobians.
Their basic body plan: two arms, two legs, sometimes wings.
Part of the split was that Chao retain morphing capabilities that Mobians usually lack - Mobians are basically ‘mode-locked’ morphers, with the mode locked before they’re born. They’re all the same species and can interbreed more or less freely (barring, like, the usual problems of say a Chihuahua and a Great Dane trying to produce puppies). Something about the genetics means that a Mobian with parents of two different ‘species’ eg a fox and a cat will generally be born as one or the other instead of a foxcat, though sometimes there’s odd bits.
It’s unclear if the ancestral not-quite-Mobians got their sapience from copying humans or if they convergently evolved sapience on their own.
Possibly this explains what the Wisps are doing - they’re temporarily un-mode-locking Sonic. I have limited experience with them since I haven’t played any games they’re in besides Generatons, though.
Also yes the planet is Mobius and they’re called Mobians, screw you
IT’S SO MUCH LESS OF A MOUTHFUL THAN SAYING ‘ANTHROS IN THE SONIC THE HEDGEHOG STYLE’ I MEAN COME ON