“A bumper sticker is an adhesive label or sticker with a message, intended to be attached to the bumper of an automobile and to be read by the occupants of other vehicles—although they are often stuck onto other objects.
“Bumper stickers can be commercial, religious, secular, humorous, or in support of a sports team or other organization. They may promote or oppose a particular philosophical or political position. In some countries, such as the United States, Bumper stickers are a popular way of showing support for a candidate for a government seat and become more common during election years.” (Wikipedia)
The Great American Conversation takes place on bumper stickers. “My child was Student of the week at ____ School” elicits “My child was Student of the Month” provokes an irritable “My child can beat up your child.”
There is the “My other car is a (Rolls Royce, bicycle)” conversation.
There is the “I brake for (squirrels, pirates, zombies, leprechauns, whales)” conversation. I brake for… wait… AAAH!… NO BRAKES!!!
There is the Christian fish symbol answered by an evolving four-legged fish. This gives way to a legged fish swallowing a Christian fish and then to an evolving fish with a Christian cross inside it, which might indicate a theistic evolutionist. You can see an assortment for sale at http://www.zazzle.com/fish+symbol+bumperstickers which proves that no matter what some people believe, somebody else can make a profit off it.