Pee is stored in the balls is a popular satirical factoid, which claims that men don’t hold their urine with their bladders, rather, their urine is contained within the testicles.
Online, the phrase usually appears as the caption to image macros.
One of the earliest instances of the claim appeared on Twitter in 2012, posted by @rad_milk, who wrote
“Apparently theres no such thing as a bladder &pee is stored in the balls &thats why I pee myself every time those teens kick me in the balls”.
Starting in 2013, posts would start emerging on Twitter as well as Reddit, asking if “pee is stored in the balls”.
The phrase started appearing on image macros in 2017 in various forms, as fake quotes on Instagram as well as captions on photoshopped images.