Hidden in an unassuming nook behind the World War II Memorial in Washington, D.C., a small engraved cartoon pays homage to the lighter side of the “greatest generation.” The little bald-headed man known as Kilroy was one of the war’s most widespread inside jokes that circulated like a meme through allied forces in the European and Pacific theaters of war.

On military bases and battlefields the world over, GIs developed a reputation for covering every surface imaginable with variations of this simple cartoon. There were Kilroys in Japan, the Philippines, France, and Italy. One mysteriously even made its way into Joseph Stalin’s private bathroom at the Potsdam Conference, prompting questions from the paranoid dictator.

The whole thing started with an American rivet inspector named James Kilroy who would scrawl his name all over the interiors of Liberty Ships after certifying parts as complete. Pat Tillery of KilroyWasHere.org described in an interview how, “sailors would [subsequently] go down into the bilges and find ‘Kilroy Was Here’ all over, in places where nobody had ever been before on brand new ships.” The unexpected ubiquity of the phrase was amusing, and people started retagging it everywhere as a sort of joke.

After arriving overseas, the troops encountered a widespread English cartoon of a bald fellow that had similar humorous connotations and the two memes were quickly joined together.

The Kilroy graffiti, “was comfort and a little bit rebellion, because they were told not to, but it spread all over the world,” says Tillery. “No matter how bad it got crawling out of that foxhole everyday, when they found a Kilroy they’d know someone was there before and survived. It was so important to every GI.”

The original cartoons were fleeting wonders, commonly drawn with fading chalk, pencil, or whatever else was at hand. It’s fitting that at the Washington World War II Memorial, two symmetrical Kilroys have been etched into the stone, one near the backside of the PA pillar, and the other opposite it. These etchings keep the little story alive, and let veterans know that Kilroy is still with GIs whenever they are in harm’s way.