A third theme might be the connection with nature. Spring fever can also be associated with a stronger connection to the natural world. In the fanfiction, Edward could be spending more time outdoors, having picnics in the park, or just enjoying the beauty of spring. This can also serve as a backdrop for his personal and emotional development, as he interacts with the environment and the other characters in this new spring - inspired setting.
I'm not sure of specific 'Edward has spring fever' fanfiction offhand. You could try searching on popular fanfiction websites like Archive of Our Own. They usually have a wide variety of fanfics, and you can use the search function to look for stories related to this concept.
Love is a very common theme. Spring often symbolizes new beginnings, so their love might be shown as growing or evolving in these fanfics. Another theme could be nature. Since it's spring, descriptions of blooming flowers, green landscapes, and fresh air are likely, and how they interact with Bella and Edward's relationship.
One popular 'bella and edward spring fever fanfic' could be 'Springtime Reunion'. It focuses on their relationship during the spring season, with beautiful descriptions of the scenery and how their love blossoms even more. Another one might be 'Spring Fever Dreams' which delves into the more dreamy and passionate side of their relationship in spring.
In a Wreck - it Ralph fanfiction centered around spring fever, we could see Ralph himself being affected. He might find that instead of his usual destructive urges, he has a new energy. Maybe he starts to build things in his own clumsy way, like trying to make a spring - themed tower out of the bricks he usually wrecks. This could lead to all sorts of comical situations with the other characters in the arcade.
If there was spring fever in the fanfiction, the characters' behaviors would likely change. For instance, King Candy might be less strict about the rules of Sugar Rush, being more lenient as the spring mood gets to him. It could also mean that the races in Sugar Rush are more chaotic as the characters are distracted by the beauty of spring in their game world.
Well, it could be about Sonic's friends trying to take care of him while he has a fever. Maybe Tails uses his gadgets to monitor Sonic's condition and Knuckles brings some special herbs that are supposed to help with fevers in their world. And Amy could be fussing over Sonic, making him soup or something.
Another theme is the connection between nature and the characters. Since spring is a time of renewal in nature, fanfic writers might explore how the characters are influenced by the changing environment, like the vampires' reactions to the blooming flowers and warmer days.
Well, in a fanfiction where Ash has a fever, it could lead to a lot of different plot developments. Maybe Team Rocket would take advantage of his weakened state and try to steal his Pokémon. But of course, his friends, like Misty and Brock, would be there to protect him. They might search for a special herb or medicine in the Pokémon world to cure his fever.