This video shows how to get the papaya hidden Angry Birds Rio Carnival Shock Level 7-8. The box is labeled on the bottom right of the level. Use the red bird first down and destroy most of the stone and wood that sits on top of the box. Then, using a similar path, breaking the remaining boxes.
The block is hiding in the lower right corner with the shipping label that has the golden papaya in it. This is quite difficult to get the golden papaya. The best way I discover to get it was to use the angry bird first to drop its egg in the hollow just before the final structure (at the top of the two blue feathers). Then you can use the red bird to bring down the blocks on the tallest structure to try to get something down on the destination box. Once you get the gold crush papaya.