Tails is very likely to help. He's Sonic's best friend and is super smart when it comes to technology. He could build a device to speed up Sonic's recovery or find a way to treat Sonic's injury. Amy is also a possibility. She's very caring and would do anything to make Sonic feel better. And Knuckles might help too. He's strong and could protect Sonic while he's recovering.
Tails would be at the top of the list. His loyalty to Sonic means he'd be dedicated to finding a cure or treatment. Amy, with her love for Sonic, would be constantly at his bedside, providing emotional support. And don't forget about Dr. Eggman. In some fanfictions, he might have a change of heart and use his intelligence to help Sonic, either out of guilt or because he realizes a healthy Sonic is more of a worthy adversary.
Definitely Tails. He's always by Sonic's side and his knowledge of mechanics and science could be crucial in Sonic's recovery. Amy would be right there as well, fussing over Sonic and making sure he has everything he needs. Cream and Cheese might also be involved. Cream is kind - hearted and could bring Sonic things to cheer him up, and Cheese could provide some comical relief during Sonic's recovery.
Hulk might be an interesting one too. Sonic's speed could either annoy or amuse Hulk. If they end up on the same side, Sonic could use his speed to lead Hulk towards the enemies. And Hulk's raw strength could be something Sonic would be in awe of. They could have a really unique dynamic, like a fast - moving pest annoying a big, strong giant at first, but then they become an effective team.
Katara would be a likely character to help Toph recover. Katara is a waterbender and has healing abilities. She would use her skills to tend to Toph's injuries, whether they are physical wounds or internal damage from overusing her earthbending. Another one could be Aang. He's the Avatar and has a deep connection with all the elements. He might use his spiritual knowledge to help Toph heal faster, maybe by finding a special place for her to rest and regain her strength.
Tails would be the first one to come to Sonic's aid. His intelligence and flying ability would be very useful in finding Sonic and getting past Eggman's defenses.
In 'my little sonic fanfiction', Sonic is definitely a central figure. He's the speedy hero that drives the action. Amy Rose is also likely to be a main character. She has a big crush on Sonic and her presence can add a lot of emotional depth and comedic moments. Shadow could also be a main character as he has a complex backstory and his interactions with Sonic are always interesting.
Sonic himself, of course. And his best friend Tails is very likely to be there. Tails is always by Sonic's side and would surely be there when Sonic is sick.
Sonic himself is always a popular character in this type of fanfiction. Whether it's Sonic from Sonic Boom or the modern Sonic, he's the central figure. Tails also tends to be popular as he's Sonic's sidekick in both versions. His intelligence and ability to create gadgets can play important roles in the crossovers.
Sonic himself is usually really popular. Whether it's the Sonic from Sonic X or Sonic Underground, he's the main hero and often at the center of the action. People love reading about his adventures and how he deals with the challenges in the combined universes.
Classic Sonic and Modern Sonic are the stars, of course. However, Knuckles can also be a very popular character in these fanfictions. His role as the guardian of the Master Emerald in the classic world and his continued importance in the modern Sonic universe make him an interesting addition. He can be the one who initially doubts the partnership between the two Sonics but then comes around. And Amy Rose is another character that often appears. Her feelings for Sonic, both Classic and Modern, can add a touch of romance or at least some emotional depth to the story.
Sonic, of course, is a must - have. But also Knuckles from both universes. In Sonic Boom, Knuckles is a bit more of a muscle - brained character in a fun way, while the classic Knuckles is more serious about guarding the Master Emerald. When they meet, there could be some hilarious misunderstandings at first, like Sonic Boom Knuckles trying to show off his strength to the other Knuckles, but then they end up teaming up against a common threat.
There could also be a group of villains working together to kidnap Sonic. For instance, a combination of Eggman and some of his more powerful robot creations along with a couple of other villains from Sonic's rogues gallery. They might have a grand plan that requires Sonic's capture, like using his power to open a portal to a world full of chaos energy that they can then control.