The Doctor has to choose between Derpy or Spitfire, but how can he when he has to save all of Equestria from Discord, Nightmare Moon, Trixie, Queen Chrysalis, Gilda, and the Diamond Dogs when they imprison the Mane Six. Maybe with a little help from Soarin', DJ Pon-3, Octavia, Lyra Heartstrings, Bon Bon, Sea Swirl, Minuette, Rose, and Amethyst Star.