Joined at the hip (or the chest, or the head, or just about anywhere else), Siamese twins are the result of a single cell that didn't quite split properly, thus creating two separate children with essentially one body.

Though joined, Siamese twins often lead very different lives. A pair in Canada who are joined at the forehead have passed their thirtieth birthday, with the more sturdy twin working as a dishwasher, and the smaller one dreaming of being a Country and Western singer. One pair in South Africa were arrested recently for violently assaulting each other, after one blamed the other for drinking too much, thus intoxicating them both.