In a 'sonic the hedgehog gets sick' fanfiction, it could be that an evil scientist created a pathogen specifically designed to target Sonic. His symptoms could include loss of his sonic abilities like the spin dash. His friends would need to team up with some unlikely allies. For example, they might seek help from Dr. Eggman's less - evil creations. They'd have to go on a quest, facing various obstacles and enemies along the way to find a way to reverse the effects of the sickness on Sonic.
One possible plot could be that Sonic catches a strange virus that slows down his super speed. His friends like Tails and Knuckles would then have to find a cure while protecting Sonic from his enemies who might see this as an opportunity to attack.
Well, perhaps Sonic gets sick because he overexerted himself during a big battle. He starts feeling weak and dizzy. In the fanfiction, the characters could explore new areas in search of a special herb or power source that can heal Sonic. Amy might be especially worried and take on a more nurturing role, constantly by Sonic's side and trying different home remedies at first.
Maybe Sonic's friends will take care of him. They could bring him medicine and make sure he rests. For example, Tails might use his inventions to find a quick cure.
In this fanfiction, the Chaotix detective agency could also play a role in taking care of Sonic. Vector might not be the best at medical stuff, but he could use his detective skills to find out the source of Sonic's illness. Espio could use his stealth to keep an eye on Sonic's surroundings, and Charmy could keep Sonic's spirits up with his energetic personality.
One possible plot could be that Sonic somehow gets transported to the Naruto universe. He teams up with Naruto to stop an evil force that is using both chaos emeralds and ninja jutsu to create chaos. Sonic's speed could be a great asset in the battles, and Naruto's determination and jutsu would also contribute a lot.
Well, the plot could involve Sonic turning into a girl due to a magical curse. In this fanfiction, Sonic as a girl might struggle with the different social expectations in her world. For example, some characters might treat her differently just because she's female. However, she still retains her brave and adventurous spirit. She might team up with some female characters in the Sonic universe who help her understand and adapt to her new form. And of course, she'll still be out there fighting Dr. Eggman, but now with a new perspective and maybe some new combat moves that come with the female form.
One possible plot could be Sonic accidentally running into the Pokemon world while chasing Dr. Eggman through a strange portal. He teams up with Pikachu to stop Eggman from stealing all the Pokeballs in a Pokemon center. Sonic's speed and Pikachu's electric attacks would make a great combo against Eggman's robots.
Well, it could be that Jack Frost is creating his icy landscapes when Sonic zooms by. Sonic is curious about this new, frosty world and Jack Frost is equally intrigued by Sonic's speed. They might start off a bit wary of each other but then realize they can team up. Maybe there's a common enemy that likes to disrupt both Sonic's green, vibrant world and Jack Frost's wintry domain. So they combine Sonic's speed and Jack Frost's ice powers to defeat this foe.
In a 'sonic the hedgehog chris pet shop' fanfiction, perhaps the pet shop is a front for an evil scheme. Sonic and Chris suspect something fishy is going on. So they start investigating. Along the way, Sonic uses his speed to dodge various traps set up by the villains within the pet shop. Chris might use his intelligence to figure out the clues. And in the end, they expose the bad guys and save the day.
Maybe in the 'sonic gets fat fanfiction', Sonic discovers a new type of power - up that gives him super strength but as a side effect, it makes him gain a lot of fat. He then has to learn to control this new power without sacrificing his speed and agility. He might go on a journey to find a way to reverse the fat gain while using the power for good.
The world would likely be in chaos. Sonic is often the main defender against villains like Dr. Eggman. Without him, Eggman could easily start taking over cities and enslaving the population. His friends would also be in a state of shock and grief, which could temporarily paralyze their ability to act.
In the 'joho gets sick fanfiction', it could be that Joho's illness is a mysterious one. His family and friends are worried sick. They search for a cure everywhere and in the process, they discover some secrets about Joho's past that are related to his current condition.