This animal is called a "pearl fish." Doesn't that sound pretty? Does it still sound pretty when you learn that they live inside the actual, literal butts of sea cucumbers (which, despite their name, are really gross animals and not plants), where they take shelter in their anal pores and eat their gonads

https://www.youtube.com/watch?time_continue=102&v=K2Eyup8Jk3w
Advertising

Didn't think so.