I am proudly still immature enough to enjoy the the below anecdote, especially the apt species name:
"Hermaphroditic marine flatworms (Pseudobiceros hancockanus) are known to duke it out to determine which one will provide the sperm and which one will receive it. These flamboyant, flowy creatures rear up and attempt to stab each other with their dual-pronged penises. The loser will be saddled with the hassle of rearing the young, while the winner gets to go off to fight another sperm-centric battle."
Find video of it, it's even more ridiculous than that sounds. My high school biology teacher showed a video of it every year, and every time it'd be the most exciting thing happening in the school that day. "Penis fencing" was the term the video used.
"Hermaphroditic marine flatworms (Pseudobiceros hancockanus) are known to duke it out to determine which one will provide the sperm and which one will receive it. These flamboyant, flowy creatures rear up and attempt to stab each other with their dual-pronged penises. The loser will be saddled with the hassle of rearing the young, while the winner gets to go off to fight another sperm-centric battle."