I heard a joke/story about a little old mexican man that for years would cross the border into the US with a bicycle loaded down with bags full of sand. The customs officials got pretty tired of having to search through all his sand and verify there were no drugs or guns hidden inside. Eventually the man stopped coming, and they figured he died of old age. But one day an officer ran into him at a bar, and asked him "Hey, all those years, we knew you had to be smuggling something, but couldn't ever find out what it was -- what was it?"

Of course, you know the punchline already, the old man said "Bicycles"