This somewhat pithy phrase can be a reference to the immortal film Casablanca. During an early scene, when the Nazi attaché Maj. Strasser (Conrad Veidt) is first testing Rick Blaine (Humphrey Bogart) in Rick's Cafe, he asks him what his nationality is. Rick replies, "I'm a drunkard." At this, Captain Renault (Claude Raines) interjects that this makes Rick a 'citizen of the world.'