And I failed to even show you the best part...
The box has an illustration of a chicken cursing from the pain of laying a square egg!
You can order yours right now for only 3 bucks right here. No promises on the cool retro cursing chicken packaging, though.
A quick inter-web search will find several egg-cubing videos, plus some photos sets and message board discussions. Apparently putting your egg in the fridge while it is cubing will help it retain the cube shape.
I also want to point out that I have refrained from using any "egg" puns this entire post. And it wasn't easy.