In defense of "Fountain", the poet Guillaume Apollinaire wrote in 1918, "The viewpoint of the Society of Independent Artists is evidently absurd for it arises from the untenable point of view that art cannot ennoble an object."  And that's a critical point here, because that's all art does, really.  We take simple, everyday materials and subect them to transformations large and small, as large as making a blank piece of fabric into a painting or as small as positioning an object in art gallery.  

These transformations ennoble these materials, making them into something more than the sum of their parts.  Like the glasses prank, "Fountain" was a test.  In 1917, it was a test to see what the institutions of the time, even the most progressive ones, could bear, and it failed.  They wouldn't exhibit it.  It was in its rejection that the object slowly rose to fame.  

The original work was lost, but Duchamp sanctioned a number of replicas later on, after his own star had risen and the urinal story persisted in art historical memory.  These replicas sit in museums around the world and still serve as a test, challenging each visitor to consider its legitimacy as a museum-worthy object.  They continue to be good barometers for us as we think about what art is, exactly, what it can be, and what we want it to be.  

Oh, hey, and one of those replicas was peed on at the Tate Modern in 2000, by collaborating performance artists Cai Yuan and Jian Jun Xi.  Actually, they only on the (?~3:36) surrounding it, in a way attemping to return the urinal to its original purpose and in hitting its barrier, highlighting how museum culture has fetishized and protected this object beyond the artist's original intentions, and while I cannot say I like or approve of this peeing performance, it does re-ask the original questions posed by Duchamp's "Fountain": What is it that makes one thing ordinary and another extraordinary?  Furthermore, it shows us that artworks, even as they sit in museums under glass, continue to shift in the way that we understand them, and let's be clear, the museum did not invite this particular performance, but museums and galleries often do invite artists to do performance-based work in the galleries, which sets up a perfect scenario for those looking to do an art prank, not that I'm recommending it.