What happens when the giant three-headed dog guardian of Hell decides to take a stroll to Ponyville? Nothing immediately relevant, except apparently the escape of an ancient, evil, magic-eating centaur monster who doesn’t even show up for two more seasons. It boggles my mind when the show creators do stuff like that, make a seemingly harmless event in one episode turn out to have major consequences several episodes, or even seasons later. Cerberus here was played off for a good joke during Twilight’s crazy time-travel antics, but the event was directly mentioned in the season 4 finale when Tirek was revealed to have escaped during that time. Joke continuity is one of the many things this show is pretty darn good at sometimes.