One possible theme could be family. As Bowser and Bowser Jr. are father - son, the fanfic could explore the dynamics of their family relationship. It could show how they support each other, or how Bowser is trying to raise Bowser Jr. to be a worthy heir.
Well, a 'bowser x bowser jr fanfic' could be about their relationship in an interesting way. It might explore how Bowser Jr. looks up to Bowser as a father figure. Maybe it shows them on an adventure together, facing challenges in the Mushroom Kingdom. For example, they could be trying to take over a new area and Bowser is teaching Bowser Jr. the tricks of the trade.
In some fanfics, there might be a plot where Bowser Jr. tries to prove himself to Bowser. He might take on a difficult task on his own, like stealing a precious jewel from a well - guarded castle. This shows his growth and determination to be a worthy heir to Bowser. And it also adds a touch of family - like relationship exploration between them.
One interesting fanfic could be about Bowser Jr. going on a solo adventure to prove himself to Bowser. He might encounter some of Mario's friends and have to use his wits to get out of tricky situations.
One common theme is family - even in their own unique way. Bowser Jr looks up to Bowsette in many of these fanfics. Another theme is adventure. They often go on quests or face challenges in the Mushroom Kingdom.
One challenge is creating a believable relationship between them. Given that Bowser Jr is often portrayed as a bit of a troublemaker from the Bowser side, and Toadette is a more positive Mushroom Kingdom character, it's hard to make their connection seem natural at first. You have to find a common ground for them, like a shared goal or a mutual understanding of a certain situation.
If such a fanfic exists, one possible theme could be the shock and chaos it would cause in the Mushroom Kingdom. The Mario characters would have to deal with this unexpected and unthinkable situation. Another theme might be about identity, as Bowser Jr. is the son of Bowser and for Princess Peach to be in this situation would completely redefine her relationship with both Bowser and the kingdom.
Sometimes, there could be original characters created by the fanfic writer. These could be other magical creatures or even some sort of mentor figure for Bowser Jr. who helps him develop his skills and understanding of the world around him, adding a new dimension to the relationship between Bowser and Bowser Jr. in the story.
Some gaming forums also have sections dedicated to fanfiction. For example, Nintendo - related forums might have threads where fans share their Bowser Jr. and Bowser fanfics. You can interact with other fans there, too, and maybe even get some recommendations based on what others have liked.
Growth and self - discovery are also common themes. He might start as a bit of a troublemaker but through his experiences in the fanfiction, he learns more about himself and grows as a character. Also, friendship can be a theme. He could make unexpected friends during his adventures, which helps him see things from different perspectives.
His father Bowser could be a major character too. He might be searching for his son throughout the fanfic. There could also be other Koopa characters like the Koopalings. They could be on a mission to bring Bowser Jr. back or they might be secretly supporting his decision to run away.