Not necessarily kid sized, just in a small size as there are plenty of grown ups who are just short. Like this stallion. He's not a colt, he's an adult stallion old enough to date Cheerilee, he's just short. Rarity being the fashion pony that she is has to make outfits to fit all body types. That's the kind of store she runs, a custom made to fit you, one of a kind, type of clothing store, kind of like wedding dresses but in a much more broad sense. And while there is Victoria Secret's Pink line for Preteens/young teenagers Like Sweetie Belle, That outfit would clearly not be from that line. At least I'm pretty sure. I don't know, I am too much of a gentleman/shy person to enter Viki's unless I had a gf to escort me. >///