Sure. Consider a fanfic set in a superhero universe. There could be a story where a hero and a villain have a contagious chemistry. Instead of just fighting all the time, their interactions become more complex. Their chemistry might be shown through their witty banter and the way they seem to understand each other's motives on a deeper level, which makes the fanfic really interesting to read. Also, in a fantasy - based fanfic, characters from different magical races could have a contagious chemistry that leads to a new alliance or a completely new story arc within the fanfic.
For instance, in a fanfic related to a famous movie franchise. There are two characters, one is a reserved and serious type, and the other is a free - spirited and adventurous one. As the story progresses, their different personalities create a contagious chemistry. They start to influence each other's decisions and actions. Their relationship becomes the central focus of the fanfic, and this chemistry spreads to other characters around them, like how their friends start to notice the change in their relationship and are affected by it in different ways.
One example could be a fanfic based on a popular TV show where two lead characters who were initially enemies start to develop a chemistry that is so strong it changes the whole dynamic of the show's plot in the fan - created story. Another might be a fanfic about a book series where two side characters have a contagious chemistry that makes the author of the fanfic focus more on their relationship than the main plot of the original book.