At first, the idea of wallpaper friends filled me with a deep and profound sadness. And then I laughed a lot. Mostly at the poorly translated English descriptions of their likes and dislikes.
http://www.single-tapete.de/maine.html (via http://imp_perfect.blogspot.com/)
The more I think about the funnier it is. I think it would be fun if they made them like giant Colorform playsets. Your living-room could be the back drop for a wild and crazy 2-dimensional party.
Personally, I can't seem to get rid of all the extra people in my house, so I can't imagine wanting to add some fake ones. Then, I also can't imagine being so depressed that I would want "Adrian" to tell me about his record collection, either.