http://www.dailymotion.com/video/x4ryo7_posterchild-companion-cube_creation someone made a real Companion Cube
Posterchild is by far my favorite street artist.* His Mario Block campaign was pretty sweet, and this new Portal installment is nice as well. The background of each portal actually shows the view out of the other, so if you found one, you could find the other. *Besides maybe Banksy.