My Little Pony: Friendship is Magic
Gender and Age
A pony’s age is simply whether they are a child, teenager, young adult, adult, or elderly. The way to say this is filly foal/colt foal, filly/colt, young mare/young stallion, mare/stallion, or nag/gaffer, respectively. For example, Apple Bloom is a filly foal, Applejack is a filly, Big Macintosh is a young stallion, Red Delicious is a stallion, and Granny Smith is a nag.
Believe it or not, nag and gaffer are not insults.