Kilroy was here

Kilroy was here is an American popular culture expression that became popular during World War II; it is typically seen in graffiti. Its origins are debated, but the phrase and the distinctive accompanying doodle — a bald-headed man (sometimes depicted as having a few hairs) with a prominent nose peeking over a wall with the fingers of each hand clutching the wall — became associated with GIs in the 1940s.