One great 'My Little Pony Applejack and Rarity fanfiction' is 'Applejack and Rarity's Unlikely Adventure'. It shows them going on a journey together outside of Ponyville and facing challenges that test their friendship. They learn to appreciate each other's differences more along the way.
To write a 'My Little Pony Applejack and Rarity fanfiction', think about their personalities. Applejack is a bit more rough - and - tumble compared to the refined Rarity. You could have a story where they swap roles for a day. Rarity has to do some farm work and Applejack tries her hoof at fashion design. This would lead to some really interesting and humorous situations. Also, don't forget to use the unique Pony language and settings to make it feel like it's part of the My Little Pony world. You can add other ponies as supporting characters too to make the story more engaging.
One great fanfiction could be 'The Adventure of Rarity and Pinkie Pie'. In this story, they might go on a journey to discover a new type of fabric for Rarity's designs, with Pinkie Pie's humor adding fun twists along the way.
One adventure was when she went into the Everfree Forest to find a special type of apple for a sick pony. The Everfree Forest is a dangerous place, full of strange creatures. But Applejack was brave. She faced all kinds of challenges, like getting lost and having to deal with some unfriendly critters. Eventually, she found the magic apples and brought them back to Ponyville, and the sick pony got better.
One interesting story could be about Rarity and Spike going on an adventure to find a rare gem for Rarity's new collection. Along the way, they face various challenges and learn more about their friendship.
The relationships of Nightmare Rarity in fanfiction are also quite fascinating. She could have a complex relationship with Twilight Sparkle, for example. Maybe they were once friends but now are enemies because of Nightmare Rarity's new form. Fanfiction writers play with these dynamics to add depth to the story.
Well, self - discovery is also a common theme. Rarity often has to learn more about herself, her talents, and her limits in fanfictions. Sometimes she might face a situation where she has to question her values in fashion or friendship. Also, magic can be a theme. As a unicorn, her magic is an important part of her character, and in some fanfictions, she might have to use it in new and unexpected ways to solve problems.
A simple plotline could be that Caramel wants to learn how to make apple products from Applejack. So, Applejack starts teaching him how to make apple jam. As they work together, they find out that they both love old pony folk songs. They start singing while making the jam, and this shared interest brings them closer together.
One common theme could be how Rarity's friends support her during her pregnancy. In the My Little Pony world, friendship is very important, so her friends like Twilight, Applejack, etc. might be there for her, bringing her food, helping with her work, and just being there emotionally.
Some common themes are loyalty and trust. Given their relationship, fanfic writers like to play with the idea of how far they'll go to trust and be loyal to each other. For example, in some stories, Spike has to keep Rarity's secrets even when it's difficult. Also, the theme of growth is popular. As Spike grows up, his relationship with Rarity changes, and this can be a rich area for fanfictions to explore. They might also face some sort of danger together, which tests their relationship and leads to new developments between them.
One great 'My Little Pony Rarity OC fanfiction' is 'The Fashionable Adventure of Rarity's OC'. It shows how Rarity's original character interacts with the existing MLP world in a very stylish way.