According to author G.M. Berrow, she named Pinkie's sisters Marble and Limestone so that they and Pinkie would have the initials "MLP", which is short for "My Little Pony". When asked on Twitter if Pinkie and Marble are twins, Hearthbreakers writer Nick Confalone replied "it comes down to your definition of twins for non-humans" and "Marble/Pinkie not identical twins, if they were I'd call them twins." Characters who have been referred to as twins include Pound Cake and Pumpkin Cake, Flim and Flam, Cheerilee and Cherry Blossom, Tofu and Tempeh, Antonio and Francesco, and Spa ponies.