Serial Killer

Have any of you seen those stickers on cars that say “serial killer”? I see these things all over the place. Most of the time I’m pretty up on pop culture, but this is really stumping me. What the hell do these mean? Are they a brand name? Is it just shock value? What’s the deal?

What column are you talking about? Other wise you are posting in zee incorrecta forum.

Moved to General Questions, where it is likely to get more responses.
Jill