Ah yes, the Cutie Mark Crusaders. What cuties! Scoot is forever grateful to Applebloom for making her that scooter from discarded barrels and a broken harvest machine. Sweetie Belle doesn’t exactly fit in, according to her sister (owner/ward, whatever sounds the most benevolent) Rarity, but only because her delicate design wasn’t exactly made for high-flying adventures that mostly end the trio without cutie marks and surprisingly often covered in oil.
Yes, Sweetie Belle being a robot is an homage to Friendship is Witchcraft, one of my favourite MLP parodies XD
Oh, and my headcanon is that Sweetie is a little smaller than the rest because… I dunno, I just think it looks like that mostly and it’s adorable ^^’