My Little Pony: Equestria Girls - Better Together Season 2 Episode 26
Lost and Pound
While checking out the various food trucks at the Starswirled Music Festival, Twilight, Fluttershy, Rarity, and Spike run into a lost and mud-covered puppy—later identified as Princess Thunder Guts. Fluttershy offers to help the dog, and she chooses one of Twilight's friends to follow.