See Stijn's post.

For my own personal explanation..
I wanted to do some sort of parody of the concept of "This is not a pipe" - while the concept is a grand one, it also wreaks to me of the pompous nature of Art. I originally just drew a cigarette - but it didn't matter, anything that really was not a pipe would have worked. I decided then to go even further from a pipe, and how better than to crudely draw a rough, crappy version of another classic piece of Art?