TIL that scientists thought Rhizocophala, a group of parasitic barnacles, were hermaphroditic, as many other barnacles. But then they discovered the "testes" were actually males living inside the f...

Almost as horrifying as cordyceps. Instead of mushroom flavor, it's the barnacle flavor that doesn't outright kill the host. I had a hard time conceptualizing the wiki article, but found a cute stop motion video explaining it.