Sonic would probably be very shocked at first. He trusts Amy, so her betrayal would be unexpected. He might initially try to talk to her to understand why she did it.
Tails would probably be very helpful. He'd use his intelligence to make sure Amy has a comfortable pregnancy, like creating special devices for her. Knuckles might be a bit awkward at first but would ultimately be very protective. He'd stand guard to make sure no harm comes to Amy and the unborn baby.
Well, Sonic is the central figure. But other characters like Amy Rose could be important. She might be heartbroken to see Sonic turn dark and try to use her love for him to bring him back. There could also be some new characters created specifically for this fanfiction. For example, a mysterious character who has the power to either make Sonic darker or has the key to bringing him back to normal.
The main characters are probably Sonic and an alternate version of Sonic. There could also be other Sonic characters like Tails or Knuckles making appearances to support the Sonics in their rescue mission. But Sonic and his doppelganger would be at the forefront, using their speed and skills to achieve the rescue.
There could also be some new characters introduced in this fanfiction. Maybe a mysterious figure who has the power to control Dark Sonic or someone who has a connection to the origin of Dark Sonic. These new characters can bring fresh plot twists and new relationships to the story.
Well, Sonic is a hero at heart. So when Amy gets hurt, he would first assess the situation calmly, but inside he'd be worried. He'd make sure she was stable and then look for the cause of her injury. If it was an enemy, he'd go after them. But he'd also be very gentle with Amy, talking to her softly and reassuring her that she'll be okay. He'd do whatever it takes to see her back on her feet again, like finding special herbs or items that could speed up her healing process.
Sonic is typically portrayed as the heroic, fast - running blue hedgehog we know from the games. He is kind - hearted and always ready to save the day. Sonic exe, on the other hand, is often depicted as a much darker and more menacing version. He might have a corrupted appearance and different abilities that are more in line with causing chaos rather than preventing it.
Tails would probably be very curious and eager to figure out how to change Sonic back. He might study Sonic's new form scientifically. Knuckles, on the other hand, would be a bit more confused but still stand by Sonic's side. Amy might be initially jealous because she's used to being the main female around Sonic, but then she could become a great friend and help Sonic adjust. Dr. Eggman would likely see this as an opportunity to take advantage of Sonic's confusion in her new form.
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.