...is when, faced with a paper tablecloth and a cup full of crayons, you and a friend decide to debate whether writing "THIS IS ART!!" does, in fact, constitute art.
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Then you roll up the tablecloth and take it with you when you leave.
(I wish I had a picture of this masterpiece in its entirety, as it was sheer brilliance. Particularly the drawing of George Costanza/Ghandi.)
(Also, Roma's, I apologize for acting like a precocious third-grader...but sometimes it just needs to be done.)