Flash Sentry could be a likely groom. He has shown an interest in Twilight in the past and they have had some interactions that could lead to a romantic relationship. Another option could be a completely new character, perhaps a powerful wizard or a prince from a far - off land who Twilight meets during one of her adventures and falls in love with.
A likely candidate could be Discord. He is known for causing chaos and mischief. He might pretend to befriend Twilight Sparkle only to betray her at a crucial moment. Another possibility is Trixie. Trixie has been jealous of Twilight in the past and could betray her out of envy.
It could be a pony who is extremely extroverted if Twilight is introverted. Someone who loves chaos and spontaneity instead of Twilight's love for order and planning.
First, you can start with his appearance. He could look similar to Twilight but have some distinct features, like a different color in his mane or tail. In terms of personality, he might be more outgoing than Twilight. For example, he could be the type to easily make friends with everypony he meets. This would contrast with Twilight who can be a bit more reserved in new social situations.
One possible fanfiction could involve Twilight Sparkle's dragon transformation being a result of a powerful magic spell gone wrong. She might struggle to control her new dragon form and powers at first. For example, she could accidentally set things on fire when she tries to use her magic in her dragon state. As the story progresses, she learns to master her new form through the help of her friends.
It could be a new character entirely. A mysterious pony who just arrives in Ponyville and catches Twilight's eye with his unique charm and different way of looking at magic.
The main difference is the 'insane' factor. Regular fanfiction might focus on Twilight's normal day - to - day adventures, like studying magic or helping her friends with normal problems. But 'insane twilight sparkle fanfiction' will likely take her into more extreme situations, like having a mental breakdown due to magical overload or some other crazy event.
Fanfiction about Twilight Sparkle being banished can also be a vehicle for exploring different relationships. Maybe she meets characters she would never have interacted with in the show. Her banishment could bring out different sides of her personality. She might become more resourceful or develop a stronger sense of self - reliance as she tries to navigate her new situation.
One great 'Twilight Sparkle Fanfiction' is 'A Magical Friendship'. It really delves into Twilight's growth in magic while also strengthening her bonds with her friends. The story has a lot of interesting plot twists and the characterizations are on point.
You can start by giving her a distinct personality. If Twilight is studious and a bit reserved, make the sister more carefree and impulsive. Maybe she has a passion for art or music that sets her apart. Her appearance could also be different in a subtle way, like a different shade of mane or a unique cutie mark.