So, Depending who is on the diaper (From front to back), you will turn into an MLP character once you wear it. Based on the mane 6/ mane 7... like: Princess Twilight Sparkle, Pinkie Pie, Rarity, Flutter Shy, Apple Jack,  & Rainbow Dash, Mystery Bonuses - Starlight Glimmer,  & Sunset Shimmer.
Pampers Easy-Ups: Kinda like a diaper, but also looks like underwear, but you slip them on pretty easily, just by pulling them up, - A "Pull-Up" aka "PottyTraining-Pants" if you will, you will be that pony.