Another idea is that Celestia's son gets lost in a different dimension. In this dimension, the rules of magic are different. He has to adapt quickly and find a way back home. While there, he meets some strange creatures who teach him new ways of using magic. This experience makes him stronger when he finally returns to Equestria.
One idea could be that Celestia's son discovers a new magic that no pony has ever seen before. He could then use this magic to help solve a big problem in Equestria, like a strange darkness that's starting to cover the land.
One interesting fanfiction could be about Celestia and Luna's early days ruling Equestria together. It might explore how they divided their duties and overcame challenges. For example, they had to deal with the first signs of Discord's chaos. Another could be a story where they swap roles for a day to understand each other's responsibilities better. And there could also be a fanfic that focuses on their relationship with Twilight Sparkle, as she learns from them.
One interesting plot could be Twilight having to go on a special quest for Celestia to save Equestria from a new, mysterious threat. Maybe it involves uncovering ancient magic.
A really cool fanfiction could be where Luna and Celestia swap roles for a day. This would lead to all kinds of chaos and hilarity in Equestria as they try to adjust to each other's responsibilities. Ponies would be very confused by the sudden change in the day - night cycle.
Some fanfictions might involve Princess Celestia in an adventure outside of Equestria. She could be on a quest to find a long - lost magic item that is crucial for the safety of her kingdom. This would show her as a brave and resourceful leader, facing unknown perils and using her wisdom and magic to overcome obstacles.
One possible plotline could be about Celestia and Luna having a friendly competition that turns into a learning experience for both of them. Maybe they compete in a magical ability showdown and in the process, discover new aspects of their own powers and each other's personalities.
One idea could be a story where Sonic accidentally runs into the My Little Pony world. He could team up with Twilight Sparkle to stop an evil force that's threatening both their worlds. Maybe a chaos - causing villain has found a way to cross between the two realms.
A more complex idea could be that an enemy from the Ben 10 universe teams up with a villain from the My Little Pony world. Ben and the Mane Six then have to combine their skills and powers. Ben uses his various alien forms to fight physically, while the ponies use their magic and friendship to combat the evil forces on an emotional and magical level.
Some fanfictions in 'my little pony bloopers fanfiction' might explore the ponies' reactions when they get their magic powers mixed up. This could lead to some really funny and unexpected situations, like Twilight Sparkle accidentally making it rain cupcakes instead of controlling the weather properly.
One idea could be a story where the prince has to go on a quest to save his kingdom from a dark magic that is slowly consuming it. He could meet the My Little Pony characters along the way and they help him with their unique abilities.
One interesting idea could be how the pony personalities translate to human characteristics. For example, Twilight Sparkle might be a super studious and intelligent girl. Another could be the relationships, like how Rainbow Dash's competitive spirit might play out in human high school sports.