If you click on the image of the envelope below, you can view a small, sixteen-page pamphlet that is intended to be put inside the postage-paid, business-reply envelopes that come with junk mail offers. Every envelope collected is stuffed with the pamphlet and mailed back to its original company.
This has been a tactic used to strike back against junk mailers for quite some time, but I have never seen it executed with such artistic vision. This is very nearly brilliant.
The pamphlet contains some adult imagery, and is probably not safe for work.