Kilroy's influence extended further than his own reach: there were lots of "woz 'ere" grafitti when I was a kid, many (if not most) of which didn't mention Kilroy — in the 1980s, a number of books of collected graffiti were published, one of which contained an observed "Lord Lucan woz 'ere", underneath which someone had scrawled "No, I wasn't".
Been a long time since I saw anything but tags any more though — the art and witticisms seem to have gone the way of the dodo and graffiti just aren't what they used to be.