Ok, lets get things straight here about the way the Teletubbies work. Facts are facts, and thats the way it is.
Lets start out by letting everybody know the sex of each.
Since there are only 4 teletubbies in all of Teletubbie land, you know as good as I do they get lonely. So we know there is gonna be some action in the land of the tubbies. Lets analyze it shall we. Po, the straight female gets boned by Dipsy, but since Dipsy is the only other male in the land, Dispy gets boned by Tinky Winky. Dipsy doesn't necessarily enjoy it, or even allow it.