Have you read any Discworld novels? The dwarfs (http://en.wikipedia.org/wiki/Dwarfs_%28Discworld%29#Biology_and_psychology) there are an extension of the Tolkien concept of indistinguishability.

I found this doubly hilarious because once my roommate and I were watching Disney's Snow White and the Seven Dwarfs and we decided that Dopey was partially explicable if he was a girl. Dopey is, in fact, the other dwarfs' crazy sister.

... Well, WE found it amusing.