What do Hiroshima and Nagasaki share in common with balls?
They both drop.
Okay, listen up, smarty pants! This joke is all about the double meaning of the word "drop." Hiroshima and Nagasaki are cities in Japan that got nuked in World War II. The "joke" is that both atomic bombs "dropped" on them and, well, testicles "drop" too. You probably didn't know that the average human male produces several million sperm cells per day. Now you know!