I'm not entirely sure what specific 'Sharing Tongues' Equestria Girls fanfiction you're referring to. It could potentially be about the characters sharing secrets or some form of communication in the Equestria Girls universe. Without more context, it's hard to analyze in detail.
Twilight Sparkle is really popular. Since she's the main character in the original series, a lot of fanfictions revolve around her adventures and her trying to adapt to the human world in the Equestria Girls universe.
One interesting story could be about a new student in Canterlot High who discovers she has a special power related to the Equestrian magic. This power helps her and her friends solve a mystery in the school.
Another theme is the clash and then the melding of different cultures. Sonic's world has a more technological and action - based culture, while Equestria Girls has a world full of magic and school - based social structures. Fanfictions often play with how these two different cultures interact. Characters might be initially confused or in conflict due to the differences, but eventually they learn to appreciate and work with each other.
One common theme is friendship. Just like in the original MLP series, the Equestria Girls fanfiction often emphasizes the importance of friendship among the characters. They face challenges together and support each other through difficult times.
In the fanfiction, there could be some kind of crisis during the graduation. Like an old enemy resurfaces and tries to disrupt the ceremony. But of course, the Equestria Girls will team up and use their unique powers and friendship to defeat the enemy. After that, they can finally enjoy their graduation in peace.
Friendship growth is also a big theme. They start out as just acquaintances or friends with some misunderstandings, but through various events in the fanfictions, they develop a deeper and more meaningful relationship.
In 'equestria girls flatulence fanfiction', it could be that some fans are exploring the more comical and less serious aspects of the characters. Maybe it's about imagining how the characters would react in embarrassing or funny situations involving flatulence. It's a bit of a strange concept but in the realm of fanfiction, people can take the characters in all sorts of wild directions for the sake of entertainment.
One great trope is the 'fish out of water' scenario. The main character from Equestria suddenly finding themselves in a human world and building a harem can lead to some really interesting and comical situations. For example, they might misunderstand human customs which then endears them to the other characters in the harem.
A really popular one is the fanfiction that focuses on Twilight's relationship with her friends in the Equestria Girls setting. It shows how they support each other through school problems, boy - girl drama, and still manage to keep their magical bond intact.