Well, the only amusing fact I have to share is that the Buddhist ordination vows are not to be given to individuals without genitalia or — and this is really funny, but I'm not making it up! — to people who change sex spontaneously (!!) or who have changed sex three or more times.
This is not meant to be discriminative! There are certain advanced practices that will only work if you are of a certain sex. Also, since the vows are different for males and females (more protective towards females, for cultural reasons: they would be far more exposed in conservative, male-dominated societies. Just travel to India today and you'll see how it is), an individual who changes sex all the time would have a hard time following all the precepts...
It's curious, however, that 2,600 years ago it was envisioned that people might, indeed, change their sex, and that wouldn't be a problem, unless you did it too often. In fact, people changing sex twice is not unheard of, although rare. But I haven't heard of anyone changing sex three times!
On the other hand, I'm pretty sure that an eunuch (who, I assume, isn't keen in full transition) who is really committed to the practice will not have the vows denied. These are actually more "guidelines" than "things written in stone". At least on the Mahayana schools, it's the intention that matters.
