pinkie strolls arround ponyville, looking for a petsitter to take gummy (she has to organize a party for somepony), but fluttershy happens to be house-sitting the bear-cave-house-while hes vacationing at the beach, so she bumps into rarity. PP-"hai rarity, have you seen anypony, i need a petsitter, oh, i know, you pet sit for me , thanks rarity, bii gummy, HAVE FUN!!!!" R-"pardon me?!"
Okay, here's my story. It's Gummy's birthday again and Pinkie, as a present for him, wants Rarity to use her fashion skills to make him a special outfit. Rarity meanwhile, having never done an outfit for any creature besides ponies, has no idea what to make of that request.