Okay, the idea begins during the final battle and final clash between Sasuke and Naruto, where Sasuke notices that this final clash of theirs will be taking more than their arms. So with his final act of redemption, Sasuke opens a dimension portal behind Naruto that pulls him through while the explosion of their final clash fully consumes Sasuke and kills him. What happens next is that the dimensional portal sends an unconscious Naruto to the MLP verse a few/couple months before the start of series and opens above Princess Celestia's royal garden while Celestia is actually there relaxing, where she finds him as her Royal Guards come rushing in.

Details I had planned for the idea:

1.) All mythical animals and animals with hooves are anthro.

2.) Naruto is still Human, which can be thanks to Naruto being a descendent of Kaguya's dimensional hoping alien clan and having Asura's chakra.

3.) The pairing was to be a Naruto x Massive Harem due to there being so many good female characters in the show that any them out felt bad to me. Ideas for why this allowed is due to their being lower population of male ponies in the world so Herds(Aka-Harems) are allowed, but not enforced thanks to magic allowing females to temporarily to have male genitalia to impregnate their female lovers so bisexual and lesbian couples more of a thing in the story.

4.) I was planning on Gender Bending some of the Male Characters like Kurama into Kurami, Spike into Barb, Shining Armor into Gleaming Shield, Discord into Eris, and etc.

5.) This is most likely going to be mature rated story depending on weather you wish to write sex scenes or not.

6.) Naruto gains the ability to use magic thanks to Sage Mode because when he gathers Nature Energy he ends pulling the magical energy that is naturally apart of it and the magic that ponies constantly use to tame said nature. This idea was inspired by reading "The Fox Scroll" by SpiritSage124, which is Naruto x Fairy Tail crossover story at FanFiction. Now at first Naruto will have to adapt with the new form of energy, but this process can be accelerated thanks to the Shadow Clone Training Method and with Kurami's(AKA-Fem Kurama) help. At first Naruto can only use magic while in Sage Mode, but with Kurami's help again, who absorbs some of magical energy as well, Naruto can produce his own magic at some point.

7.) The Royal Guards are a lot more competent and reliable in this story because I hate how they are practically useless in the show.

8.) Princess Celestia and Princess Luna will be Goddess Levels of Power in this story as well with Godly Powers representing who they are. Princess Celestia being the Goddess of the Sun and Daytime. Princess Luna being the Goddess of the Moon, Nighttime, and Dreams/Nightmares, which make the battle between Naruto and her when she is Nightmare Moon an epic battle if you are imaginative and good at writing fight scenes.

9.) Kurami(AKA-Fem Kurama) has become a Semi-Juubi with all the powers/abilities of the other Tailed Beasts when arriving into the MLP Dimension due her absorbing the borrowed chakra that her siblings gave to Naruto during the 4th War and them not being able to return to original owners thanks to them now being in a separate and not connected dimension. Also Kurami will start taking on an anthro form in order to blend in with the other anthropomorphic creatures, tho she will have a Human Appearance as well, but doesn't use until the events of first Equestria Girls, which will get a humorous react from Naruto and Kurami responding with a foxy grin saying he never asked. I was thinking this would have dramatic effects on her appearance and I did find an OC Nine Tails drawing by one artist including having a human form that perfectly represents her change in appearance into a Semi-Juubi. Links to said drawings will be added later.

10.) Of Course since the good guys are getting a big boost in power so will the villains in order to make thinks still difficult for the good guys. An Example, the Changelings can turn their bodies in weapons or armor like the two main characters from the Prototype video game series, tho added with magical power/energy included as well to their transformations.

Okay, I will be taking another break and will hopefully add more of ideas/details soon.