Fun request!

What’s better than one brain? Thirty-two brains! That’s how many brains a leech has. Their bodies are separated into 32 segments, each with its own brain fragment. In addition, each leech has 10 stomachs and nine pairs of testicles, as well as a set of ovaries.

(Image: A pair of mating tiger leeches (Hirudo medicinalis) by David Hemprich-Bennet)

Hirudinea. This subclass is made up of leeches, soft worms that are typically parasitic and feed on blood

Bonelliida. In this order of unsegmented marine worms, the males are much smaller than the females, and typicaly live on or inside them.

Leech

No clue what kind though.

Unidentified, subclass Hirudinea

Did you know that most annelids (marine worms, earthworms and leeches) are hermaphrodites; having both "male" and "female" reproductive organs? Terrestrial and marine worms can reproduce both asexually and sexually, but leeches can only reproduce sexually. And guess what? They have penises. Well, some of them.

For example, the family Gnathobdellae transfer sperm this way. They reproduce by having two individuals basically rub up against eachother, with their heads facing in opposite directions; this allows contact between one Leech's "male" gonopore (a genital pore in the side of the body), and the other Leech's "female" gonopore. This allows a leech to transfer a spermatophore, which is basically a little packet of sperm cells, to the other leech. The miracle of life, everyone.

Bonus fact: Earthworms have prostate glands. I'll leave you to think about that one in your spare time, though.