The history of "Kilroy Was Here".

Interesting article on the history of "Kilroy Was Here" - historians have even tracked down the original Kilroy. I liked this part:

Japanese troops were so mystified by a "Kilroy Was Here" painted on a bombed out tank on the Pacific island of Guadalcanal that they reported the find to their senior intelligence officers, according to a U.S. Marine interviewed by World War II author Timothy Benford.

Hitler supposed that Kilroy was some kind of "Super-GI" or spy, other unconfirmed reports have stated, and ordered a contingent of men to track down the sneaky American. He would never be found.

Article here.