For our daughter's 5th birthday, we held a LEGO-themed party. A highlight of the party was the huge pile of 75 giant LEGOs. The giant LEGOs were made by painting cardboard moving boxes in the classic primary LEGO colors. They kept a dozen five-year-olds (and plenty of excited parents) occupied for a couple of hours. Building with the blocks was great, but, of course, knocking them down was even more fun.
Since DUPLO is twice the size of regular LEGO, QUATRO four times, and these blocks are about ten times that size, we've decided to call them DECCO. Just moved, and looking to reuse your boxes? Make DECCO!