That’s my evening gone:
“At 165888 x 79872 pixels, or 1.3 terapixels, the image would fill the screens of 4212 iPads with retina displays in an 81 x 52 grid. The grayscale image is 12.3 gigabytes in size. If it was printed at a size big enough that you could see the people, it would cover a football end zone. And as you might expect in a Randall Munroe comic, there are little treasures to be discovered all over the place. I don’t want to spoil the fun, but yes, Waldo’s in there too.”
http://www.comicmix.com/webcomics-you-should-be-reading/2012/09/19/xkcd-click-and-drag-the-biggest-comic-ever/