A friend of twin trolls, Ash and MK, claim they say the word "prune" while getting their picture taken to achieve the perfect pout.
Another source could not confirm this explosive new tidbit of information. They told OK! (via MSNBC), “It could be true (that they say prune) but unfortunately I can't say — they like to keep their personal lives personal. They do care about their smiles though. Mary-Kate has slightly thinner lips and more of a playful grin, while Ashley tends to go for a full-on pout. It has been the obv(ious) way to tell them apart for years.”
They probably chose the word prune because that's the only thing they eat all day. The source could have also heard wrong. They were really saying the word "poo" because their laxatives were starting to kick in.