Once upon a time, two faced people and one faced people lived on earth together in harmony, even though the one faced people didn't know it. You see, the one face people were an aggressive race that didn't like anything that was different, so the two faced people had to come up with something to hide their faces; they made a contraption that looks like modern-day bra's, but they put it on their faces to hide one of them, and most of the other. The one-faced people thought this was weird, but the two-faced people made up a lie, saying that they were doctors and needed them to protect them from disease. While sort of true, the overall aspect of it was a lie. Anyway, females of the one face people thought, since they were tired on the men eyeing their chest all the time, figured that the two faced peoples masks would work as a perfect way to cover them up, so a group of one faced people went in their houses and stole their masks while they were asleep. They also noticed that they had two faces. This started a war, but since there were more one faced people than two faced people, the one faced people won and annihilated all the two faced people. This is why there are almost no two-faced people on earth anymore. This is why women wear bra's. And this is why that the doctors mask thing looks like like a cup thing.
tl;dr: Ponies are cool.