SpY is a urban artist hailing from Madrid. He has been working since the mid eighties, but has been popping up a lot on the blogosphere lately. He has been called "The Banksy of Madrid," although I disagree because his style is unique and just because Banksy is very popular doesn't mean we need to compare everyone to him.
According to his website SpY's pieces want to be a break in the automat-like inertia of the urban dweller. Bits of thought that hide in a corner for whoever wants to let himself be surprised. Full of both irony and a positive sense of humor, they appear to inspire a smile, a thought, to help a conscience a little bit more lucid.
Although he started primarily as a graffiti artist, he has branched out into public installations such as these, adding a bit of humor to the urban landscape around him.