bad wolf in dr.who was meant as a message for the doctor that the fabric of space time is about to explode/implode or whatever could happen that would end time it self
Except that's not even nearly right
Rose left 'Bad wolf' scattered across the universe as a sign to her past self, it was her way of telling herself she was about to do the right thing by wiping out the daleks
The Doctor Who fanclub at my university went around writing Bad Wolf and Spoilers and Don't Blink on like EVERYTHING. They even did a giant mural of an exploding TARDIS in chalk. Grabbed a picture for my Whovian friend in California.