I had a whole bag of Cocoa Puffs that had gone stale, and thought it would be fun to mess around and see if I could bake something with them. So I aimed for muffins. I more or less based it on a banana muffin recipe I make all the time:  2 1/2 cups ground Cocoa Puffs (I used this to replace both flour and sugar) 1 tbsp baking powder 1/4 tsp salt 1/3 cup vegetable oil 1 egg 1 cup milk 1/2 cup vanilla yogurt (I figured this plus extra milk would make up the mass, pH, and moisture content of the bananas)  I didn't really expect it to go well, but I figured I'd probably have bad muffins, not this:  The batter was stretchy, like less-sticky bread dough. I spooned it into paper cups and baked it at 400ºF. At first they looked like they were puffing up as expected, then they looked a little imploded in the center and shiny on top, then one by one they burst and started dripping everywhere. I expected 20–25 minutes but had to pull them out at 15. The aftermath was soft but cohesive and a little rubbery, not at all hard to clean. So, lesson learned: Cocoa Puffs are not flour. But what chemical reaction happened or didn't happen to make it go this wrong? 
Muffins and cakes rise because of chemical leavening agents and the expansion of hot gasses, they stay risen because the flour and sugar forms a structure which traps the air, then solidifies enough to hold its shape once the expansion has stopped. Cocoa puffs are made in a process called extrusion, where batter is pressurized and shot out in little spurts. On the release of this pressure the little squirt of batter expands and almost crystallizes in the same way as a muffin or cake, in other words puffs are cooked by a different method, but the processes which make them hold their shape is the same. These processes aren't reversible, you can't turn a cake back into flour, milk, sugar and eggs. Grinding up cocoa puffs is essentially the same thing as grinding up dried cake, they may absorb some moisture but as the chemical and physical changes involved in crystallization have happened it won't happen again. What it looks like is that your batter expanded enough to go over the top of the muffin pockets and then outward, then collapsed because there was no structure to keep the shape. 