You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own (AO3). Just use the search bar and type in 'Naruto MLP crossover' and you'll get a list of relevant fanfictions. Some might be really creative, like imagining Naruto characters in the world of MLP or vice versa.
One interesting plot idea is the transfer of Naruto's ninja skills to the ponies in the MLP world. Imagine a pony using shadow clones or rasengan. It's a really cool concept that combines the action - packed nature of Naruto with the colorful and magical world of MLP.
I really like 'Pony Tail Adventures'. This fanfic delves deep into how the MLP characters would interact with the Fairy Tail guild. It has a lot of humorous moments as well as some heart - warming interactions between the two sets of characters. For example, Twilight Sparkle and Lucy Heartfilia become fast friends and go on adventures together, exploring the unique aspects of each other's worlds.
Friendship is a very common theme. In these crossovers, Sonic, who is often portrayed as a bit of a loner in his own world, gets to experience the strong friendship bonds that are central to My Little Pony. He learns about working together with the ponies and the value of having friends.
Check out blogs dedicated to MLP fanfiction. Some bloggers review and list their top picks for crossover fanfictions. They often provide summaries and their own opinions, which can help you decide which ones are worth reading.
Maybe the Avengers are shrunk down to the size of ponies and end up in Equestria. They have to adapt to the new world and its rules. Iron Man could try to build new tech using Equestrian resources, and Captain America could use his leadership skills to form an alliance with the ponies against a common threat, like a dark magic - based enemy that wants to take over both worlds.
Transformation can also be a theme. Maybe a Thomas character gets transformed into a pony - like form in the MLP world or vice versa. This can lead to humorous situations as they try to adapt to their new forms and the rules of the new world. It also allows for exploring how their identities change and how they are perceived by others in this new state.
It could be about Link ending up in Equestria and teaming up with Twilight Sparkle to fight a new evil that threatens both their worlds. Maybe Ganondorf has found a way to enter Equestria and is causing chaos, and Link uses his combat skills while Twilight uses her magic to drive him out.
The characters can also develop through shared experiences. For instance, if they go on a quest together, they will face challenges that force them to rely on each other. Ponies might teach Lucario about the joys of celebration and relaxation, while Lucario could teach the ponies how to be more vigilant and face danger bravely. This mutual growth would make for an engaging crossover fanfiction.
A possible plot could involve a dark force threatening both the world of Lucario and Equestria. A group of ponies and Lucario have to come together. The ponies use their magic and the Lucario use their combat skills and aura powers to fight off the common enemy. This would show how different abilities can be combined in a crossover story.