Flatworms have male and female sets of genitalia, and if they can’t find a flatworm to mate with, they will inseminate themselves by stabbing their head with their needle-like copulatory organ, a practice known as selfing. – WTF Fun Facts
Source: https://www.cnet.com/news/this-flatworms-freaky-sex-life-will-freak-you-out/
