One of my favorite things in the whole wide world is when people have a conversation via graffiti. When I was 17 I remember reading the following interchange on a desk in the Notre Dame University library.
Person 1: "God is dead." —Nietzsche
Person 2: "Nietzsche is dead." —God
I thought that was the most hilarious thing I'd ever read at or on a library desk. A few years ago I saw where someone had written in a toilet, "Free Mumia" and someone else had modified it to read "Free Mumias to the first 100 customers!"
I just saw this photo of a piece of public art by British artist Banksy and it made me smile. Who doesn't want a complimentary wine of their choice? Such smart and funny political humor! Banksy does a lot of prints and paintings as well as public art, see below.