When he was nine, Harry became a unicorn when he fell through a portal into the Everfree Forest outside Ponyville. Now, the Goblet of Fire has hauled him back to Hogwarts, still as a unicorn. A unicorn taught by Twilight.
When Apple Bloom, Sweetie Belle, and Scootaloo goes to vist Zecora to see if she has any ideas for getting their cutie marks. They end up falling into her brew and were reborn as the Powerpuff Fillies!
Harry Potter, after a beating by Dudley and friends — with the help of a real gang member — wishes he had somewhere safe to go, and starts crawling home. He ends up in Equestria. The CMC find him. A year later, an owl brings his Hogwarts’ letter!
When the CMC asked Discord to help them attend magic school, he pulled an owl out of his hat. Only he didn't exactly have a hat. Which was okay, since their new school had a singing one laying around. Where the hay was Hogwarts anyway?
The Crusaders have finished their first semester at Hogwarts with the second about to start. The Weasley twins may be taking bets on how many professors take up heavy drinking by the end of the year.