The unaltered poster, and samples of altered posters with drawings and photocopies added to the blank white space. Posters in the subway are made of self-stick plastic now, replacing paper and wheat paste in the last 5 years. It's very easy to take a pen knife or even your house key and cut out sections of these posters and replace the image elsewhere. That's how the images of superman and crocodiles were added to the blank space in the Mad Men posters to mashup and reinterpret the design.
I love New York City and I really love how these altered posters takes the controversy right out of the falling man icon that's been a part of Mad Men's fantastic ad campaign and corporate identity program (befitting a top advertising agency) since day one.