Omega

The Kilroy doodle seems to have first appeared as the "Australian Foo" during World War I. Kilroy gained notoriety in the US before World War II, however, and a similar "Mr. Chad" was appearing in England at the same time. The doodle is rumored to have derived from the Greek symbol for Omega, and conveyed the same meaning of "someone is watching". At some point shortly before the outbreak of World War II, it seems, Australian Foo, Mr. Chad, and Kilroy merged into the classic "Kilroy was here."