An old Egyptian joke my uncle told me.

At a border between two cities, a police officer sits in his hut, managing the border.

One day, a man comes riding on a bicycle with two bags. The police officer looks through the bag to find only sand. He gives the man on the bicycle a weird look, but tells him to pass. After all, it's only sand.

The next day, the same man on the bicycle passes through the border once again, with two bags. Again, the officer looks through them to find only sand. Another weird look, and the man passes through the border.

The police officer isn't the smartest of people, realizing the man could have been smuggling something within the sand.

Two days later, the same man passes on the bicycle, with two more bags of sand. The officer feels through the sand, finding just rocks this time. The officer is now just plainly weirded out but still lets him pass.

Two other events where the man on the bicycle passes through the border occur, and the officer is starting to get fed up more and more each time.

He pulls a gun on the man, asking violently, "Tell me what you're smuggling right now or your brains are blown off."

The man calmly replies, "Bicycles."