After the events of Enies Lobby, the straw hat crew set off on their next adventure, however after saving a girl named Twilight Sparkle, she begs for their help to save her kingdom from a legendary pirate named Kate Jones.

Isaac is an ordinary guy from the UK, who was living a normal life, just going through his days, playing online games, and watching good old fashioned anime. One day, a mysterious package arrives for him in the mail from something called the Lobelia Organization. When Isaac opens this package, he finds a strange looking Fruit with a swirly pattern inside. Soon after opening the package, Isaac is transported to the world of Equestria, appearing within the Royal Garden. 

Meanwhile, Princess Celestia is hosting the annual Grand Galloping Gala, when suddenly, she senses the arrival of something strange and dark, little knowing that her Kingdom is about to be changed forever. 

This is the dawn of a new age. 

The Age Of Devil Fruits.

Star Swirl "The Bearded One", known as the King of Equestria, passed away. But before dying, he communicated that he will leave his kingdom to the strongest pirate in the world.
Thus, hundreds of pirates from around the world will compete to reach Equestria, among whom is a young rookie pirate named...

Twilight Sparkle, "The Starry Crown"

Fluttershy is quite the expert on creatures of all shapes and sizes, including ponies. So, as you can imagine, the sight of a walking talking skeleton pony with an afro might give her pause.

Side story/midquel to My Little Pony: Nakama is Magic.

One can expect to find many new friends on the high seas when you're the Straw Hat Pirates. New adventures await them as they journey to new locations. Meeting new creatures and ponies. And discovering how big their world truly is. Adventure is out there, you only need to extend your hoof out to meet it!

First series - post-S1 - 2 Parts
Part 1: "A Fairy Tail Misadventure"
Islands usually don't pop out of the ocean, right? When one does such, the Straw Hat Pirates begin a magical journey in the country of Fiore. However, not all is well within this country. And there is much that even their new friends don't know about.

Part 2: "An Ultra First Encounter"
A storm out of the blue - and a melodic sound - send the Straw Hat Pirates to a new and unfamiliar island off their course. Here there be strange creatures unlike any they've ever seen. Will they be able to survive this encounter? Or could these be new friends on the journey of life?

Luffy lands nearby Ponyville due to a fight that happened not so long ago. During his stay, he encounters, befriends, and soon has adventures with six certain ponies that will shake Equestria.

One Piece X My Little Pony Crossover
Teen Rating - Multiple use of cuss words.
Gore - Bits of bruises and cuts, nothing too serious.

Part 1 - Introductions
-Chapters 1 to 7
-Luffy's arrival attracts curiosity of the ponies as he demonstrates his numerous abilities causing a disruption of peace. Though not meaning to do trouble, he gives the six ponies the next few days they'll never forget.
Part 2 - Ponyville Arc
-Chapters 8 to 16
-Luffy finally makes a move that will plunge all of Equestria into war. Alliances will be revealed as well as actions no one ever knew about until now, and the fate will be determined by Luffy and his crew's actions.
Part 3 - Griffon Arc
-Chapters 17 to ???
-The time to enter the war is now. Luffy along with Twilight and the rest of the team will go into Griffon turf in order to end the feud as well as finding the rest of the Straw Hats.

Takes place after two year time skip
Takes place before Discord was freed and wreaked havoc
Inspiration and better story in the link.
One of the many One Piece X My Little Pony crossovers with potential
Ace-Catel the artist