One common theme is friendship. Since they are two different characters, exploring how they become friends is often a central part. For example, they might start off as rivals and then slowly realize they have more in common than they thought.
Another theme is growth. Both characters can grow individually and also in their relationship. Maybe Jessie is initially shy and Delia helps her come out of her shell, and in the process, Delia also learns something about herself.
One common theme could be friendship development. Maybe they start as rivals or strangers and gradually become friends. Another theme might be adventure, where they go on some sort of journey together.
One common theme is the idea of redemption. Giovanni, being a villain in the main Pokémon series, often has a journey towards redemption in these fanfics, especially in relation to Delia. Another theme is the exploration of their different worlds colliding.
One common theme is family. Their relationship as mother and son is often explored deeply. Another theme is growth, like Ash's growth as a person and how Delia influences that.
Another one could be 'Jessie and Delia: A New Beginning'. This fanfic starts with them meeting in an unexpected situation. As the story progresses, their friendship blossoms into something deeper. The story is well - written, with detailed descriptions of their emotions and interactions.
One of the main themes is growth. Ash's growth as a trainer is often related to Delia's influence. Also, the theme of homecoming is popular. Ash coming back to Delia in Pallet Town after his adventures is a frequently explored idea. These themes help to build a more emotional and relatable story between them.
Friendship is a very common theme. Most patsy and delia fanfics explore how their friendship grows and overcomes obstacles. It shows their loyalty to each other.
I'm not sure where to specifically find Delia x Jessie fanfiction. You could try searching on some popular fanfiction websites like Archive of Our Own (AO3). They have a wide range of fanfictions and might have some for this pairing.
A frequent theme is the relationship development. It usually starts with an initial encounter, like Delia accidentally stumbling upon Springtrap. Then, it progresses through stages of mistrust, curiosity, and eventually, some form of connection. There's also the theme of survival. In some fanfictions, they are in a dangerous situation together, and their relationship is tested as they try to survive whatever threats are in the FNAF world.
One common theme is friendship. Jessie and Lemon are often depicted as having a strong bond. Another theme could be growth, like they grow as individuals through their experiences together.
Friendship is also a big theme. Despite their initial enmity, fanfics often explore how they can become friends or at least have a more amicable relationship. For example, they might work together to achieve a common goal in the Pokémon world.