A good fanfic of them should have their distinct personalities shine through. Rainbow Dash's confidence and athleticism, and Pinkie Pie's wackiness and friendliness. If it can capture that essence, it's a great start.
Character development is key. Maybe Pinkie Pie learns to be more responsible in some aspects while Rainbow Dash learns to be more open - minded. Also, a good plot that involves both of them equally. It could be something like they have to find a lost magical item that's important to Ponyville. Along the way, they face challenges that test their friendship and individual strengths. There should be a balance between the two characters' storylines and how they interact with each other. Their banter and the way they support or annoy each other can make the fanfic really engaging.
The setting of Equestria should be well - described. It adds to the charm of the story. In a Rainbow Dash and Pinkie Pie fanfic, the author can use the unique locations in Equestria to create interesting scenarios. For example, if they are in the Everfree Forest, Rainbow Dash can use her flying skills to scout ahead while Pinkie Pie uses her knowledge of the forest's secrets (maybe she knows some friendly creatures there) to help them navigate. Also, the fanfic should have a good message about friendship, loyalty, and laughter, which are the traits associated with these two ponies.
In a Rainbow Dash and Pinkie Pie fanfic, it could be centered around their shared experiences. Maybe they enter a competition together. Since Rainbow Dash is competitive and Pinkie Pie loves to be involved in things, this could lead to some really interesting scenarios. The story might also explore how they deal with their differences. For example, Rainbow Dash might get frustrated with Pinkie Pie's chaos at times, but then realize that it's part of what makes her special. And of course, there will likely be lots of colorful descriptions of Equestria and the other ponies they interact with.
Character development is key. In these fanfics, we often see Rainbow Dash becoming more in - touch with her softer side thanks to Pinkie Pie, and Pinkie Pie might become more responsible with Rainbow Dash's influence. Also, the fanfic should capture their unique personalities well. Rainbow Dash's competitiveness and Pinkie Pie's wackiness should be on full display.
Friendship is a very common theme. Since they are both characters from the MLP universe, fanfics often explore how their friendship develops and grows. They might start as acquaintances and become best friends, or they might have some bumps in their friendship that they need to overcome.
Adventure is also a popular theme. They might go on a quest together, like looking for a lost treasure or saving Ponyville from a mysterious threat. This allows for a lot of action and character development. In these types of fanfics, Rainbow Dash's bravery and Pinkie Pie's spontaneity often play important roles.
Another interesting one is 'When Pinkie Met Dash'. This fanfic delves into their first encounter and how it led to the development of their relationship over time. It has a lot of cute and humorous moments that really capture the essence of their personalities.
There's also 'Rainbow Dash and Pinkie Pie: Unlikely Allies'. In this fanfic, they start off on different paths but end up coming together to solve a big problem in Ponyville. It delves deep into their personalities and how they complement each other. It's quite long and detailed, which is great for those who like to really get into the story. The descriptions of their emotions and the situations they face are very vivid.
There are quite a few 'rainbow dash x pinkie pie fanfic' out there. Some focus on how they support each other during tough times in Ponyville. Like when there was a big storm and Pinkie Pie used her cheerfulness to lift Rainbow Dash's spirits, and Rainbow Dash in turn protected Pinkie Pie from the strong winds.
Good character development. Show how Scootaloo grows in confidence with Rainbow Dash's help. Also, an exciting plot. Maybe something that involves flying challenges or a mystery to solve. And of course, the friendship between them should be at the core, like how they support each other through tough times.
A good MLP Rainbow Dash harem fanfic often has well - developed characters. Each member of the harem should have their own distinct personality. For example, if Pinkie Pie is in the harem, she should be as bouncy and fun - loving as in the original series. Also, the relationship between Rainbow Dash and her harem should be believable. It can't just be forced for the sake of having a harem concept.
Good 'pinkie x rainbow dash fanfic' usually has well - developed characters. It shows Pinkie's bubbly and unpredictable nature and Rainbow Dash's confident and competitive side. For instance, Pinkie might come up with a wild plan, and Rainbow Dash has to figure out how to make it work in her own way.