'Who is Kilroy?'

During the World War II, the phrase 'Kilroy was here' began to appear wherever US troops were. It was often accompanied with the image of a face with a long nose and two big round eyes with small dot eyeballs peeking over a wall or a line representing a wall. Everything else, except sometimes his fingers gripping the top of the wall, was hidden behind the wall itself.
Kilroy is a familiar image, whose origin is something of a mystery. In 1946, the American Transit Association had a radio programme called Speak to America. This programme sponsored a nationwide contest in an attempt to solve the mystery behind the origins of the mystical Kilroy. Speak to America found James J Kilroy of Massachusetts as a result of their search. That James J Kilroy was the originator of 'Kilroy was here' is currently the most commonly believed explanation for the phenomenon.
James J Kilroy was a ship inspector at the Fore River Shipyard in Quincy, Massachusetts, USA. It was his responsibility to check on how many holes a riveter had filled in a shift on any given day. In order to prevent double counting by dishonest riveters and to prove to his supervisors that he'd been doing his work, he began marking 'Kilroy was here' inside the hulls of the ships being built. He used yellow crayon so it would be easily visible; this way the off-shift inspectors wouldn't count the rivets more than once and pay the riveter for work he hadn't done.
Once the ship became operative, carrying military troops that were headed overseas and bound for the war, the phrase was a complete mystery. Why it was there and being found in such out of the way places made it all the more mysterious. All they could be certain of was that Kilroy, whoever he was, had 'been there first'. As a joke, troops began placing the graffiti wherever the US forces landed and claimed it had already been there when they'd arrived.
Whoever originated it, Kilroy quickly became the United States super GI who had always already been wherever men were sent by the military. The game quickly became a challenge to put the picture and slogan in the most unlikely places imaginable first.
According to author Charles Panati, it's supposed to be atop Mount Everest, on the torch of the Statue of Liberty, on the underside of the Arc de Triomphe in Paris, on the Marco Polo Bridge in China, on huts in Polynesia, on a girder on the George Washington Bridge in New York and scrawled in the dust on the moon. Panati also wrote that an outhouse was built, during the Potsdam Conference in July of 1945, for use exclusively by Roosevelt, Stalin and Churchill. The first of the three to utilize the facility was Stalin. Upon emerging he inquired of his nearby aide, 'Who is Kilroy?' This was supposedly overheard by a translator and is where the story comes from.

Kilroy and Hitler - The Rumour

Near the end of World War II, Adolf Hitler was absolutely and completely paranoid regarding one insurgent in particular. This individual seemed able to get into everything and anything that was thought to be secure in Nazi, Germany. He (Hitler) ordered his best men to begin actively searching for this super-spy and all troops were commanded to shoot and kill this menace.
The 'spy' Hitler was looking for was none other than Kilroy! GIs in occupied territory and spies in the German Army were vandalizing Nazi bases and equipment with the Kilroy logo and its well-known slogan. It wasn't intended as anything more than graffiti and a prank, but by the final year of Hitler's reign, he was convinced Kilroy could penetrate into any secure area and feared for his own safety thinking Kilroy was certain to kill him.

Origins

Oddly enough, as widespread as the Kilroy phenomenon was there is no concrete evidence to verify either when or where it began, nor who began it in each country (USA, England and Canada). In England, the Kilroy logo was known as Chad and his slogan consisted of 'Wot no...?' The blank was usually filled in with whatever there was a shortage of or whatever was being rationed at the time. The Oxford English Dictionary states that Chad's origin is obscure, but that British Cartoonist George Edward Chatterton may have created it. Though the James J Kilroy story seems to be the most likely point of origin for the 'Kilroy was here' legend, there is possible evidence of occurrences of the Kilroy logo much earlier than World War II.
Though Chad was popular in England, just as Kilroy was in the US military, still nobody (other than James J Kilroy) has stepped forward to claim him as their own invention, even though there were 26 men named Kilroy in the military during WW2. There was also a Canadian version known as Clem and in the late 1960s there was a version in Los Angeles, California that went by the name of Overby. Perhaps the theory of Kilroy being an unknown super soldier wasn't so far off after all...