In case anyone cares.
1. Antoine is a hamster
2. The Freedom Fighters (besides Rotor) are not North American/European species of animals but North African/Middle Eastern species.
3. Tails’ mother was a Freedom Fighter who was captured after he was old enough to remember her (which is why he says he misses her in Sonic Past Cool).
4. Robotnik wants to make everything mechanical because he hates the chaos and disorganization of biological life (cannon to early Archie) and hates Sonic in particular because his reckless, unpredictable perseverance embodies everything he wants to control, but can’t. This is why he becomes more and more obsessed and unhinged as the series goes on and Sonic continues to succeed.
5. Snively is not inherently evil like Robotnik but has Stockholm syndrome, possibly from earlier abuse (seriously, who names their kid Snively?), which is why he ended up with his uncle in the first place.
6. Robotnik never uses roboticized family members against the FFs because he didn’t keep good records on who/where each person was - he assumed a quick victory and didn’t think their identities would matter. Related, he either only recently figured out how to access roboticized Mobians’ memories or else lied to Uncle Chuck about being able to, because he otherwise would have easily found Knothole’s location from roboticized FFs.
7. Mobius is it’s own planet entirely, no Plant-of-the-Apes style Earth-in-the-future lazy world building. It opens up more possibilities and makes it easier to accept when biology and physics don’t match up with reality. Ex: Robotnik doesn’t use satellites much because the gravity/radiation/magnetic field/etc. of the planet and surrounding astronomical bodies makes them not very effective.
8. Sonic is demisexual.
9. Bunnie already had unusual strength, and robotization only enhanced it, and her robot parts extend internally, allowing her to support the weight she’s able to lift. Robotization in general enhances physical abilities.
10. Roboticized Mobians don’t need to eat or sleep, though they can, but do need to recharge. There are the equivalent of charging stations in the areas where they are kept.
11. A deroboticized person is healed of any injuries they had before being roboticized.
12. Much of the FFs (and Knothole’s) clothes and equipment come from all the abandoned stores, buildings, and warehouses in Robotropolis, so most things took effort to get (hence their wearing less clothes than when they were younger). Sonic probably goes through shoes quickly and has multiple pairs of the same sneakers that he got after finding a shoe store on a mission.
13. All of the FFs still participate in keeping Knothole a functioning village and know basic skills like growing and storing food, cooking, sewing, repairing a range of items, etc. Despite this, Rosie still often has meals prepared for them when they get back from missions.
14. Sally doesn’t use her title as Princess, and the respect she gets as a leader is because of her experience (basically cannon; the Sally-bot’s line “I am a Princess, but out in the Great Forest, titles are meaningless” actually comes from Sally’s description in the series bible).
15. Season 2 Rotor didn’t happen. I realizes this is basically everyone’s headcannon, but just to be clear, it’s mine too.
16: The “dragons” are not dragons at all, but monotremes. Egg laying with pouches? Seemingly normal-length lifespan? Duck-bill-like face? No apparent scales and what resembles hair on some? Seemingly the only fantasy-based animal we meet? Maybe they’re really flying platypus. If hedgehogs can be blue and run fast, and foxes can fly using their tails like a helicopter, platypus can be green, have wings, and breath fire and ice. (OK, this one’s not really a headcannon, just an amusing thought that Gojira007
convinced me to include)