1) Character 2) Fictional character 3) Fictitious character 4) Furtive graffiti guy 5) Guy who was here 6) He was here 7) The man who was here 8) Ubiquitous man 9) WWII graffito 1) Doodle 
[n] - a nonexistent person popularized by American servicemen during World War II
a fictitious American male, created by American troops who left the inscription “Kilroy was here” on walls, property, etc., all over the world in the years during and after World War II.