"Penis-Fish," or, "wow, nature is a mind-fuck, isn't it?"

Male phallostethids have a unique complex copulatory organ, termed the priapium, under the throat (thus the fishes of this family are commonly called "priapiumfish"). The priapium is a bilaterally asymmetric organ for holding or clasping onto females and fertilizing their eggs internally; following internal fertilization, phallostethid females do not give birth to live young, but instead lay fertilized eggs.

Scientists don't yet understand the evolutionary origin of the unusual placement of the fish's reproductive organ.

via 'Penis-headed' fish discovered in Vietnam," news.mongabay.com