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