International relations, as it were.

An American and a Canadian are sitting together on a plane. After takeoff, the Canadian leans back, takes off his shoes and begins to relax. The American, who's penned in at the window, says, "Sorry to trouble you, but my call light is broken. Could you get me a beer?"

"No problem," says the Canadian and heads for the galley to get the beer, at which point the American bends down and spits in the Canadian's shoes. The Canadian returns with the beer and settles back into his seat.

Upon landing, the Canadian puts on his shoes and immediately realizes what has happened. "Ah, hell," he asks the American, "why does it always have to be this way? This constant fighting between our nations, this animosity, this spitting in shoes, this pissing in beers ..."