In addition to RuPaul and Oscar de la Hoya, you can now add a whole slew of male animals who aren't above masquerading as female for safety, a chance at mating, or just a little same-sex body contact.
In a New York Times essay released yesterday, James Gorman mentions several of mother nature's transvestites. The stars of the story are a population of Western marsh harriers in which 40% of the males have the same plumage as the females. While we grant that the hawks didn't pick out their feathers the same way some of us may pick out a feather boa and falsies, they do behave like female hawks as well—this means they only attack other females and they're safe from male attacks. Most scientists guess this behavior is all rooted in an attempt for the males to have an advantage when mating—no one ever said a cross-dresser has to be gay.
Even better was a story about the male garter snake, who will sometimes emit female pheromones after emerging from their homes in the winter. These pheromones are strong enough to attract "enough males to give them a snake-hug," and, duly satisfied and warmed from a bit a friction, the sneaky snake shuts off the scent.
Take a look at the New York Times essay here—it manages to be that rarest of things—witty and factual, with references to Eddie Izzard and Some Like it Hot, to boot.