Can You Guess How This Art was Made??

It uses a common office supply?
Well if you haven't guessed it by now all of these artistic creations were made using Post-it notes. Any guesses as to how many post-its you would need to cover the walls of this room??
Or would something simple like these be more of your style??
Or would you be up to the ultimate challenge like this one that covers several floors of an office building??
What are your thoughts on this? Is it even art? What type of character or picture would you make if you had the chance?