The fanfiction could go like this. Sonic is on a mission in a spooky, abandoned town. Unbeknownst to him, it's infested with vampires. One of them manages to turn him into a vampire. At first, Sonic is horrified. His appearance changes slightly, with paler fur and redder eyes. He has to learn to live with his new condition. His friends like Tails and Knuckles are confused and a bit scared. However, Sonic discovers that being a vampire gives him the ability to sense danger from afar. He then uses this to his advantage to protect the town and his friends from an even greater evil that's lurking in the shadows. Eventually, he might find a way to reverse the transformation and return to his normal self.
His speed might become more of a stealthy movement. Since vampires are often associated with being sneaky, Sonic could use his speed to silently move around, like a shadow. Also, he might gain the ability to hypnotize enemies, which he could use to stop bad guys in their tracks before using his speed to quickly deal with them.
One common element in the Sonic turns into Dark Sonic fanfiction could be the role of antagonists. They might have a hand in triggering this transformation. For example, by manipulating Sonic's emotions or by using some sort of dark magic. Once Sonic becomes Dark Sonic, his relationships with his friends like Tails and Knuckles also change. His friends may try to bring him back to his normal self, which can create a lot of drama and action in the fanfiction.
Sonic turning into a robot in fanfiction could also be a self - sacrifice situation. Suppose there's a powerful energy source about to explode and Sonic, in order to contain it, fuses with some nearby robotic parts. This would give him the ability to withstand the blast but at the cost of his normal form. His friends would be shocked at first but then try to find a way to restore Sonic. It could lead to an interesting adventure filled with emotions and high - stakes situations.
If Sonic turns into a robot in fanfiction, he might gain new abilities. For example, he could have enhanced strength and more precise control over his speed. However, he might also face problems like being hacked or having mechanical malfunctions. His friends like Tails would have to use their technical skills to help him out.
The plot might involve Sonic being turned into a Pokemon by a powerful wizard in the Pokemon universe. As a Pokemon, he retains some of his speed abilities but also has to learn Pokemon moves. He meets a group of friendly Pokemon trainers who help him understand this new world. Together, they enter Pokemon battles against other trainers and gym leaders, all while Sonic tries to find a way back to his own world.
One possible plot could be Sonic accidentally getting hit by a strange energy beam during a battle with Dr. Eggman. This beam could have some sort of mutagenic effect that slowly starts to transform him into a human. As he turns into a human, he has to deal with the loss of his super speed at first. He then has to adapt to living as a human while still trying to protect his friends and the world from Eggman's new threats.
A common theme is the clash of two different worlds. Sonic represents speed, freedom, and heroism, while vampires often symbolize mystery, darkness, and immortality. So, there's often a struggle when these two meet.
Another theme is the relationship with his friends. In 'sonic the vampire fanfiction', his friends might be scared of him at first, but then they learn to accept him. Also, there can be a theme of power. His new vampiric powers can be both a blessing and a curse, and the stories often explore how he uses or controls them.
One common theme is the clash of two different worlds. Sonic's world is usually very bright, fast - paced and full of adventure, while the vampire world is often dark, mysterious and associated with danger. So when they come together in fanfiction, it creates a lot of interesting conflicts.