The greatest trick the devil ever pulled was convincing people he didn't exist. The second greatest was convincing people that MLP is for little girls only.
Twilight fails at solving a riddle and nearly destroys civilization... we think. Honestly, still not sure really WHAT happened, beyond the fact that she lost her bucking marbles. Oh yeah, something about a riddle. And Pinkie Pie. And insanity. Yeah.
The whole day was going so far so good for Rarity. She had a full stock of dresses that were ready to be sold. But, this "normal" day is going to change when a... "unique" costumer visits the Carousel Boutique.