Posterchild is the nom de plume of a street artist based in Toronto, Canada who is best known for his Mario Blocks project, the purpose of which is to install homemade Mario blocks in public spaces. After being featured on Boing Boing the project has expanded as others have made and hung their own blocks. Currently Posterchild also runs his own website, called Posterchilds Blade Diary. The term comes from the fact that graffiti stencils are cut using a blade. Wikipedia
The definitive Wikipedia entry for Posterchild. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Posterchild_%28street_artist%29