Look up "anglerfish reproduction". The males are tiny and permanently fuse themselves to a female, basically becoming a parasite of balls.
Wikipedia:
When a male finds a female, he bites into her skin, and releases an enzyme that digests the skin of his mouth and her body, fusing the pair down to the blood-vessel level. The male becomes dependent on the female host for survival by receiving nutrients via their shared circulatory system, and provides sperm to the female in return.
Look up "anglerfish reproduction". The males are tiny and permanently fuse themselves to a female, basically becoming a parasite of balls.
Wikipedia: