S1·E19 A Dog and Pony Show

To create jewel-encrusted clothing at the request of a famous pony, Rarity decides to find a new lode of gems with Spike's assistance. But when a group of creatures called the Diamond Dogs abduct Rarity and force her to find gems for them, Spike and the other ponies head underground to rescue her. In the end, who will be the one that truly needs saving?