The combination of a beaver-like body and duck-like bill of the platypus (Ornithorhynchus anatinus) is only the first of a long list of strange features on this unique creature. These odd mammals also lay eggs, have venomous spurs, sense electricity, glow under UV light, and harbor five times more sex chromosomes than many other animals. Now, a study published in Biology Letters reveals that their fur also contains melanosomes that are unlike in any other animal—and scientists can't figure out why.