I recommend reading My Little Phantom, Friendship is Ghostly by Etrigan the Demon and Phantom Fan 21 if you haven't yet. Fantastic story! https://www.fanfiction.net/s/10370834/1/my-little-phantom-friendship-is-ghostly

Phantom and Twilight are headed to the world of Canterlot High as they retrieve their crowns from Sunset Shimmer and her little sister, Moonrise. With the help of some friendly ghosts and the power of friendship, can they work together with their new friends to stop them or will they lose their crowns to two ponies who want to rule Equestria? Read along to find out.