Ah, the famous In 'n' Out 21x21, done in style by unityxx. He had to construct it with 3 x 7x7's, but would unityxx have the stamina to finish this towering burgery challenge?
From: http://www.youtube.com/watch?v=NnN4bPOhCj4
I ate the 21x21 burger at In-N-Out, on 03.04.2006. 21x21 means 21 patties and 21 slices of cheese. Unfortunately, they had to bring it out as 3 7x7, instead of 1 huge one.