What are the rules to 'punch buggy'?

Have you ever been driving or walking down the street with a friend and for no apparent reason he punches you in the arm and says "Blue Punch Buggy, no punch-backs"? No, he hasn't developed a nervous tic; he's playing the Punch Buggy game.

The rules are simple: Whenever you see a Volkswagen Beetle, as quickly as you can, turn to the person nearest you, punch their upper arm firmly, yet gently, and say the color of the car, followed by "Punch Buggy". Remember to say "no punch-backs". If you don't, someone else can punch on the same car, a situation to avoid.

And if you have the fortune of seeing a convertible Beetle, you can punch twice. Rules about specific colors and consequences of stating the wrong color vary from region to region. You'll know soon enough if you and your friend have different rules regarding red Bugs, for example. The same applies when you're watching a movie in which a Punch Buggy appears. And if you've rented The Love Bug, it is strongly advisable to establish the rules before watching it.