Well, it's hard to say for sure without reading a lot of them. But perhaps themes of friendship could be common, as Mitch and the crab interact. Or it could be about a unique adventure they go on together.
Well, Danielle Jonas and Kevin Jonas met and were attracted to each other. As they got to know one another better, they realized they had a strong connection. They went through the normal relationship stages like dating, getting to know each other's families. Eventually, they decided to tie the knot. Since then, they have been building a beautiful life together. They are a great example of a couple in the public eye who seem to have a very stable and loving relationship.
Some Tumblr blogs might also feature 'stephanie x mitch fanfic'. There are many fanfic enthusiasts on Tumblr who share their work or reblog interesting stories. You can search relevant tags like #stephanie x mitch fanfic to find them.
I'm not sure where to specifically find Mitch x Crab fanfic. You could try searching on popular fanfic websites like Archive of Our Own. There might be some creative stories there.
Without reading the actual story, it's hard to say. But there could be a group of seagulls that are always around the big fish and Jonas. They could act as messengers or observers in the story. There might also be a fishmonger in the local market who has heard rumors about the big fish and is interested in it. Additionally, there could be a mermaid or some other magical being that has a connection to the big fish and Jonas's story.
One popular 'stephanie x mitch fanfic' might be the one where they go on an adventure together. It could involve them exploring a mysterious forest and facing various challenges that bring them closer. It often has elements of friendship turning into something more.
I'm not sure who Mitch Campbell is without more context. There could be many people named Mitch Campbell. Maybe he's a character created specifically for this story.