On another thread we've been discussing a bumper sticker, and I've got questions.

First, wasn't sure that I'd got my interpretation right because we're not big on bumper stickers here, except for "Baby on board", I guess. But I've heard about bumper stickers in other countries. Are they meant to define the driver, the car, to be quirky, or funny, or inspirational, or everything at once? Are there different genres of bumper sticker?

Then, are they only called "bumper stickers" when they go on the bumper? I've seen the ones which are stuck on the inside of the back window; are these also called "bumper stickers" or something else?

Last, bumper sticker discourse seems to be language at play to a great extent, with ambiguities, cross-references, double meanings, metaphors... have you got any interesting examples which you'd care to share?

EDIT: I've just checked and there are a couple of historical threads about bumper stickers on the board already, but I think they are more about specific sticker texts, so I still put forward my more generic questions... Having said that, I note the undebatable convenience of checking first and posting afterwards!