In nature's coolest collage experiment, Platypuses are like the result of throwing together the leftovers from a bunch of other animals. They're the only mammal to lay eggs, they have venom in their feet, they don't have nipples so they sweat milk to feed their young, and now it turns out they glow in the dark as well.
"Scientists are seeing the Australian platypus in a whole new light. Under an ultraviolet lamp, this bizarre-looking creature appears even more peculiar than normal, glowing a soft, greenish-blue hue instead of the typical brown we're used to seeing.
Over the centuries, biofluorescence has been reported in various plants, fungi, fruits, flowers, insects, and birds. It's only recently, however, that scientists have begun to actively track down examples in the animal kingdom."
The Mystery of the Platypus Deepens with the Discovery of its Biofluorescent Fur.
As of yet, it's unclear why they glow in the dark. Researchers think it might help camouflage the platypus from other UV-sensitive nocturnal predators (ravers?) or prey by absorbing UV light instead of reflecting it.