Edward and Bella are the main characters that should be in a Twilight first kiss fanfic. However, Carlisle can also play an important role. He could be the one who gives Edward some advice about his relationship with Bella and the significance of the first kiss. Rosalie could be another character to include. She might be skeptical or even jealous of Bella and Edward's relationship, which can add some conflict. And don't forget about Esme. Her motherly love for Edward can provide a different perspective on the whole first kiss situation.
Obviously, Edward and Bella are must - includes. They are at the center of the first kiss. But adding other Cullens like Alice can be interesting. Alice could have premonitions about the kiss and her reactions or attempts to influence the situation can add depth. Also, Jacob could be included. His unrequited love for Bella can create some great tension. He could show up at an inopportune moment just as Edward and Bella are about to kiss, leading to a very tense scene.
Well, of course, Edward and Bella are essential. But including some of the Volturi members could make for an exciting fanfic. Aro, for example, could somehow be aware of the impending first kiss between Edward and Bella and have plans related to it. It could be that he wants to use this moment to manipulate the Cullens. Then there's Jessica, Bella's friend from school. She could be the one who accidentally witnesses the first kiss and then spreads rumors, which causes all sorts of problems for Edward and Bella in the human world of Forks.
Alanna and George are the core. But a mysterious wizard could be included. The wizard could be a bit of an obstacle at first, perhaps casting a spell that causes some misunderstandings between Alanna and George. This would create tension and drama in the story. And then there could be a young apprentice who is trying to learn from the wizard but also befriends Alanna and George. The apprentice can help to resolve the misunderstandings in the end, leading to Alanna and George's first time together.
Sonic himself is a must - include. His speed and adventurous spirit drive the story forward. Tails is also great as he can provide technical support and is Sonic's loyal friend. And Dr. Eggman, as the main antagonist, always adds conflict and excitement to the story.
Vegeta is a great choice. His rivalry with Goku adds a lot of drama and action to a fanfic. Also, Piccolo, as he has a long history with Goku and has been both an enemy and a friend. Another good character could be Gohan, Goku's son, as it can explore their father - son relationship further in the fanfic.
Another good character to include is Lex Luthor. He could be the mastermind behind a plot to drive a wedge between Batman and Wonder Woman. His devious mind and resources would make him a formidable antagonist, and his interactions with the two heroes would add a lot of drama to the story.
Optimus Prime is a great choice. His leadership and wisdom can add depth to the story, and his relationship with Bumblebee can be explored further. Also, Sam Witwicky, as he has a strong bond with Bumblebee in the movies. Their friendship can be a central part of the fanfic.
Definitely Naruto himself, as he is the main character of the original series. Sasuke is also a great choice as his complex relationship with Naruto can add a lot of drama. Kakashi is another good character to include. His wisdom and unique abilities can be very useful in the story. And Sakura, her growth as a ninja can be explored further in a fanfic.
Well, obviously Armikasa themselves are the main focus. But you could also include their friends. For example, their comrades who are with them in training or on missions. These characters can add more depth to the story by providing different perspectives and interactions.
Nami would be a great character to include as she has a deep - rooted history with Arlong. Their interactions can add a lot of drama and emotion to the story. Luffy is also a good choice as he is the main protagonist and his values of freedom and justice would contrast sharply with Arlong's tyranny.
Obviously, Willy Wonka himself is a must - include. He's the heart and soul of the factory. Charlie Bucket is also great as he represents the pure - hearted visitor. The Oompa - Loompas add a lot of fun and mystery with their strange songs and unique appearance. Veruca Salt can bring in some drama as she was the spoiled brat in the original story.
Fluttershy could also be included. Imagine a scenario where Trixie is trying to put on a big, bold magic show and Fluttershy's timidness contrasts with that. Twilight might be caught in the middle, trying to make sure Fluttershy doesn't get too scared and that Trixie doesn't feel like her show is being ruined.