From the site:
We’d go and sit on the balcony at Terminal 3 at Heathrow Airport, directly under one of the PA speakers where we put a tape machine in a bag with the microphone poking out of the top. Then we’d look for a flight that had arrived in the last 40 minutes from somewhere where you’d expect people with unpronounceable names i.e. Saudi Arabia.
We would then go to the Airport Help Desk with a pre-written note containing the names of fictitious passengers and ask them to read out the names over the PA system.
The passenger’s names looked innocent enough on paper but they sounded like something else when read out loud.
For example: Looks like: Makollig Jezvahted and Levdaroum DeBahzted. Reads Like: My colleague just farted, and left the room, the bastard. The site has sound files as well. Good stuff.