One possible plot could be that Flash Sentry has always had a secret crush on Twilight Sparkle. After Twilight saves Equestria from a great danger, Flash finally musters the courage to confess his feelings. Twilight, who has also grown to like Flash during their adventures together, reciprocates, and they share a sweet kiss.
In a more complex plot, Flash Sentry could be from a different part of Equestria where there are some political tensions. Twilight Sparkle is sent as an ambassador. Flash is initially assigned to protect her. Over time, they overcome the differences between their regions and their own personal insecurities. Their relationship develops, and the kiss could be a significant moment that symbolizes the union of their two worlds and their love for each other.
Maybe there's a magical mishap. For example, a spell goes wrong and Flash Sentry and Twilight Sparkle are the only ones who can break it. In the process of trying to reverse the spell, they get to know each other on a deeper level. They realize their mutual attraction and end up kissing as a sign of their new - found love. This kind of plot can add an element of mystery and adventure to the fanfic.
Perhaps it's a story about their friendship being tested. Flash Sentry gets an important mission that takes him far away from Ponyville. Twilight Sparkle is worried about him and has to deal with her own insecurities. In the end, their friendship prevails as Flash Sentry returns safely and they realize how much they mean to each other.
Another possibility is that the fanfic is set in a time of crisis. Flash Sentry and Twilight Sparkle are called upon to use their unique skills to save Equestria from a powerful enemy. Along the way, they face challenges that test their friendship and loyalty, and in the end, they emerge victorious and with a stronger bond.
You can try searching on fanfiction platforms like Fimfiction or Archive of Our Own. These sites have a large collection of My Little Pony - related fanfics, and there's a good chance you'll find stories about Flash Sentry and Twilight Sparkle kissing there.
A plot could involve Flash Sentry and Twilight Sparkle teaming up to organize a magical event in Equestria. However, things go wrong when a jealous pony tries to sabotage their plans. They must then work together to overcome the obstacles, find the culprit, and still make the event a success. This would show their problem - solving skills and how their different personalities complement each other.
One popular storyline could be Flash Sentry helping Twilight Sparkle adjust to some new situation in Equestria. For example, when a new magical threat emerges, Flash Sentry, with his courage and Twilight's vast magical knowledge, they team up to face it. Another could be a story about their friendship developing over time. Flash Sentry might initially be in awe of Twilight's magic, and as they spend more time together, they learn more about each other's strengths and weaknesses.
The theme of magic also plays a big role. Given Twilight's strong connection to magic, fanfictions may show Flash Sentry being in awe of her magic or even having some sort of magical encounter himself because of her. Also, the theme of growth, both personal and in their relationship, is quite common. They start from being acquaintances and grow into a couple or very close friends over the course of the story.
One common theme is the exploration of an unlikely relationship. Since Flash is more of an ordinary pony compared to Twilight's powerful and studious nature, fanfics often focus on how they bridge that gap.
Often, these fanfictions highlight the contrast between Twilight's intellectual and magical side and Flash Sentry's more physical and practical side. This contrast creates interesting interactions and relationship building.
Maybe the fanfiction could explore a magical accident that results in a baby - like entity being created between Twilight and Flash Sentry. They then have to figure out how to take care of this new being while also trying to reverse the magic if it's not meant to be. For example, they might seek the help of Princess Celestia to understand what happened.
Well, it could be about Twilight Velvet using her charm to get Flash Sentry's attention. Maybe she shows off her intelligence or her unique talents. It might involve some kind of mystery or adventure that they go through together, with Velvet leading the way in seducing Flash.