This is truly excellent, since it has a very pertinent point that's obvious when you see it - pink soldiers are no accident, no little boy left them behind.

"Kilroy was here" is similar, but maybe more organic, since it was propogated by many different people spontaneously.

When I was at Purdue a long, long time ago, somebody wrote this mysterious slogan all over campus, in bathroom stalls, on sidewalks, any flat surface: "Chocolate pudding wrestle with a long silky haired girl". That was a little disturbing.