A group of programmers and marketers were traveling to a trade show on a train. Each of the marketers had bought a ticket, but the programmers had only bought one ticket for the lot of them.
One of the programmers was keeping a lookout, and when the conductor neared their car he called out "The conductor's coming!" and all of the programmers piled into the train's lavatory and closed the door. The conductor took the tickets of all of the marketers, and then knocked on the lavatory door and called "Ticket please." The programmers slid their ticket under the door, and the conductor took it and left.
The programmers were laughing at the marketers for the rest of the trip, and the marketers felt like idiots.
On the way back, the marketers decided they would use the same trick and only bought one ticket for them. But this time, the programmers didn't buy a single ticket! Again, one of the programmers kept a lookout for the conductor. When he called "Conductor coming!" all of the programmers piled into one lavatory, and all of the marketers shut themselves into another lavatory.
One programmer came back out of his lavatory, knocked on the other door, and said "Ticket please!"