Foo was here is an Australian graffiti signature of popular culture, especially known for its use during World War II, but also became popular amongst Australian schoolchildren of post-war generations.
Foo is shown as a bald headed man (sometimes depicted with a few hairs) peering over a wall (usually with the fingers of both hands appearing to clutch over the wall as well), with the simple inscription "Foo was here".
One source says of Foo that "He was chalked on the side of railway carriages, appeared in probably every camp that the 1st AIF World War I served in and generally made his presence felt. If this is the case, then "Foo was here" pre-dates the American version of World War II, "Kilroy was here", by about twenty years.
It has been claimed that Foo probably came from the acronym for Forward Observation Officer, but this is likely to be a backronym.