Definitely Doofenshmirtz. He has such a complex and comical personality. His backstory and his constant attempts at evil - doings, which always seem to backfire in a hilarious way, make him a great character to write about. Perry the Platypus is also interesting. His double life as a secret agent adds an element of mystery and action to any fan fiction.
Phineas and Ferb themselves are very interesting to write about. You can explore their creative minds further and come up with even wilder inventions for them. Perry the Platypus is also great. His secret agent life is full of potential for exciting stories. And Doofenshmirtz, with his wacky plans and his complex backstory, can be a really fun character to write about in fan fiction.
One popular theme is alternate universes. For example, fans might write about what would happen if Phineas and Ferb were in a world where they didn't have their usual resources but still had to build amazing things. Another theme is character relationships. There could be stories exploring a deeper friendship between Perry and Doofenshmirtz, beyond their usual nemesis - hero dynamic. Also, time - travel is a common theme, like Phineas and Ferb going back in time to meet their ancestors and how that changes things in their present world.
The Sole Survivor is a very interesting character to write about. Their backstory of losing their family and then emerging into the post - apocalyptic world gives a lot of room for character development. Codsworth, the friendly Mr. Handy, can also be interesting. You can write about his loyalty to the Sole Survivor and his unique perspective on the world. Another is Nick Valentine. His synth nature and detective skills make for great storylines, especially when he's solving mysteries in the wasteland.
Well, it really depends on the writer's preference. But if we consider the main characters, Van Pelt has a lot of potential. Her journey from a newbie in the team to a more experienced agent can be explored in many ways. Her relationship with Rigsby, and how she balances her personal and professional life. Another interesting character is the psychic that Jane sometimes consults. There's a lot of mystery around that character, and fan fictions can expand on his abilities, his relationship with Jane, and how he fits into the overall world of The Mentalist.
I think the antagonists in 'the gifted fan fiction' can be really interesting to write about. They often have complex motives for their actions. Maybe they are using their powers for a cause they believe in, but that goes against the heroes' values. Their backstories and how they came to be the way they are can add depth to the fan fiction. Also, the side characters with more subtle powers can be great to write about as they can surprise readers with their abilities in unexpected situations.
Mal is definitely one of the most interesting. She has such a complex personality, being the daughter of Maleficent. There's a lot to explore in terms of her struggle between her mother's dark legacy and her own desire to be good. Evie is also great. Her journey from being a'spoiled' princess - type to someone more independent and kind - hearted can be really fun to write about. And then there's Jay, with his thieving ways but also his potential for growth and loyalty.
Chuck himself is very interesting to write about. His transformation from a regular guy to a spy is full of potential for different storylines. Sarah is also great. Her mysterious past and her relationship with Chuck can be explored in many ways.
Clark Kent is obviously one of the most interesting. He has so many layers to his character, from the shy farm boy to the emerging superhero. His internal struggles with his powers and his moral compass make for great writing. Lex Luthor is another. His complex personality, with his intelligence and his slow descent into darkness, gives a lot of room for creative interpretations in fan fiction.
Definitely Edward. His complex nature as a vampire who is trying to resist his baser instincts while being in love with a human makes for great material. Writers can explore his internal struggles in more depth. Also, his past and how he became a vampire can be elaborated on in fan fiction.
Well, I think Mr. Bun, Calvin's stuffed bunny, could be an interesting character in fan fiction. There could be stories about his 'life' when Calvin isn't around. And Rosalyn, the babysitter, is also a great character to write about. Her battles with Calvin are classic, and fan fiction could expand on those moments. But overall, Calvin and Hobbes remain the central and most fascinating characters, as their relationship is the heart of so many possible stories.