When I was an undergraduate, at McGill University, there was much made in Montreal of a Magritte exhibition at the Musée de Beaux-Arts. The museum put on a fierce ad campaign, and all the papers -- even the student press -- did news stories and reviews.
Part of the press kit, I guess, was an image of La trahison des images, the painting that was also featured in many of the museum's advertisements. For several weeks in Montreal, the words "Ceci n'est pas une pipe" were everywhere.
Now, at the same time, a different exhibit was on in the city. Avi Friedman is one of McGill's more celebrated professors, an instructor in the school of architecture specializing in clever ways to house poor people without demeaning them. Essentially, he's spent most of his career figuring out how to make the absolute most efficient use of residential space.
One of his projects was a three-story house that, as I remember it, could contain three families comfortably in some ludicrously small area. Like, 400 square feet or something, for a family of three or four. They'd actually built a prototype version and put it up on the quad, with furnishings and everything. I checked it out once, and though it was definitely cozy inside, it certainly didn't feel cramped.
The night before it was to come down, however, in what I thought was a brilliantly cerebral act of vandalism, somebody spraypainted on the side of it, in big black cursive letters: "Ceci n'est pas une maison."
I seemed to find that much funnier than most other people did.