Actually, platypuses (platypi?) were quite normal looking in the early days. They looked pretty much like beavers. But then, one day, the Platypus Supreme Court ruled that restricting marriage to a union between male and female platypuses was unconstitutional. The descent into madness started with male platypuses marrying each other, but eventually some began to turn a lustful eye toward the ducks who inhabited the same waters, and the rest is history.
How Gary-Larson-esque.