Yes, there are some out there. You can start by looking on fanfiction websites. Some might focus on their unique relationship, perhaps in a setting where they have to team up against a common enemy in the Mushroom Kingdom and develop an unexpected bond during the adventure.
The fact that it's an unexpected pairing. Most people might not think of them together at first. But in fanfiction, it allows for creativity. Writers can play with the idea of love or friendship blossoming between two characters who seem so different, like a story where Toadette helps Bowser Jr. see the good in the Mushroom Kingdom and its inhabitants.
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.
Some fanfictions might take a more comical turn. Picture Bowser and Bowser Jr trying to host a party in their castle but everything goes wrong. From the invitations getting lost to the food being ruined, it's a hilarious take on their characters.
One possible storyline could be that Bowser Jr and Toadette start off as rivals. Bowser Jr is always causing trouble in the Mushroom Kingdom, and Toadette is one of the ones trying to stop him. But as time goes on, they start to understand each other better. Maybe Bowser Jr realizes that his actions are causing harm and Toadette sees that he's not all bad. They could end up teaming up to solve a bigger problem in the kingdom, like an invasion from a new enemy.
One good bowser jr x cody fanfiction might be one where they team up in an adventure. Maybe they have to overcome some obstacles in a strange land together.
You can try fanfiction websites like Archive of Our Own or FanFiction.net. They have a wide variety of fan - created stories, including those about Bowser and Bowser Jr.
Another option is Archive of Our Own (AO3). In some fanfictions, their relationship could be a slow - burn one. Maybe they start off as rivals, constantly competing in some sort of multi - character tournament. But as they get to know each other better, they start to develop feelings.
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.
There are many bowser jr fanfictions out there. For example, 'The Great Bowser Jr Quest' where he goes on a quest to prove himself to his father, Bowser. It's full of action and shows his determination. Also, 'Bowser Jr's Secret Talent' which reveals a talent that no one expected him to have, adding a fun and unexpected twist to his character.
One good 'bowser jr and peach fanfic' could be one where Bowser Jr. has to learn about kindness from Peach. For example, he might get lost in the Mushroom Kingdom and Peach helps him find his way back to his father, Bowser. Along the way, he starts to see her not as an enemy but as someone with a good heart.