Posey is the 1980s pony that Fluttershy was based on. Tended to plants the way Fluttershy does animals, and is generally as sweet as you'd expect. However, she's not as shy as Flutters is. If you watch the original series, it's more like Fluttershy is part Posey and part Sweet Stuff. (Sweet Stuff isn't as well known as the likes of Firefly or Surprise, but she had the "selfless to the point of being taken advantage of" problem and had a hard time seeing her own worth. Fluttershy could teach poor Sweetie some assertiveness, I kid you not...)