Proportionally biggest testicles.

Image by Richard Richards, University of Derby

Oh dear. The Tuberous Bushcricket (Platycleis affinis) has the biggest testicles in proportion to body weight of any animal. They take up 13.8% of its overall mass. That's like a man having some 22 pounds (10 kilos) of pure testicle. Overall that is, not each.

The output is actually quite low, though. It appears that the cricket uses its stature to mate with a larger number of females rather than devote lots of energy to just one.

This does not serve as a role model for human males to follow.

More on the bushcricket with massive testicles.