I stole a pile of labels from work and wrote many weird things on them with a sharpie. I later went and stuck them all over a local theatre, and one of them was PLA related. I harassed a friend of mine who works the concession to give me one of those 'special water cups' that taste like coke, but she wouldn't go for it, so I waited for her to turn away and I stuck a label reading 'The PLA pwnt your mom last night' on the til. It was there for several nights after that, and so was one I put on a payphone reading 'OMG HAX'.
UPDATE: that story is really lame...don't bother reading it. What WOULD be cool however would be if the image on the media DVD that says 'The PLA used this payphone to annoy the hell out of somebody' became a sticker.