It's not big, but it's very clever. In short - there's a series of LEGO builders who have taken to building (small) models, whilst they're still in the bag they came in!
Here's an example of it being done with 30010, Fire Chief.
What impresses me is that I won this set recently (Yay for London AFOLs!) and built it _out_ of the bag. I found it impossible since the height of the minifig exceeded the stress the bag would take. My solution was too literal, and I should have had him stood down on the lower step, to make it possible.
Thanks to Justin for highlighting the link to me!