Neatorama has a post up titled 37 Fads That Swept the Nation – how many do you remember?

Kilroy Was HereKilroy Was Here
And here. And here. During World War II, Kilroy was everywhere. Accompanied by a cartoon of a large-schnozzed man peeping over a wall, the “Kilroy Was Here” [wiki] phrase graced everything from the Arc de Triomphe in Paris to hut walls on Polynesian islands. So who was Kilroy? Turns out, he was probably Navy shipyard inspector James J. Kilroy, who reportedly scrawled the phrase onto parts he’dKilroy Schematic examined. Sailors later made a game of the enigmatic phrase, vying to be the first to impersonate Kilroy in a newly liberated era. In fact, “Kilroy Was Here” became such a ubiquitous military fad that Apollo astronauts are said to have written it in the dust on the moon.

H/T to Charming, Just Charming for the link.