It's a famous saying in in Italy on the problem of losing information when averaging

"If one person eats a chicken and another person doesn't eat anything, on average they both ate half a chicken"

Or in a similar way something like:

"If I eat two chickens and you eat none, statistically we both ate one"

In Poland we use "on average, me and my dog have three legs"

In Latvia, we say "on average, all have no potato." Then we are sad.

The rest is only hallucination from malnutrition and death

I dunno, I saw lots of potatoes in Riga!! :)

The saying dates back to before the discovery of the New World, when in fact no one in Latvia had potatoes.

In America we have: "The man who has feet in the freezer, and his head in the oven, on average feels fine!"

An average human only has one testicle.

Not sure where I heard that.

The average male human has less than two testicles.

Also, the average human has less than two legs and less than two arms.

This reminds me of this old joke: https://news.ycombinator.com/item?id=1089588

To expand, it comes originally from a poem from Trilussa[0], a poet which wrote satirical poems in the Roman dialect. I'm afraid they lose a lot in translation.

[0] http://www.fotografi.org/studi_settore/polli_di_trilussa.htm

I'm guessing stats where the basic question doesn't reflect reality. "If a chicken and a half lays an egg and a half in a day and a half, how many eggs will three chickens lay in thirty days".