really cool

the theme is simple and strong, and having the world be composed of cardboard really drives it home. The Amelie music fits really well too. The graphic quality could be improved a lot though - even though you can tell you used cardboard, the perspective is off, so you don't get the 3D feel that cardboard should give.
Have you heard of a book called Cardboard Universe? It's really cool, about what I think you're aiming at here: how fragile the walls of 'reality' are

Real cardboard?

This was great to look at because it was just so authentic! I kind of doubt that it was done with actual cardboard, but still great. I think my favorite effects would have to be when you cut outside the box and see the sky. It's especially fun to see each of these objects just pop up. Some of the sides look a little crude, but it's still great to look at. The music was also suiting as it gave you a sense of being shown something very high class.

It was an experimental flash, so it didn't seem to have much of a plot for me. I didn't care though, because it was so great to look at. There's just a great sense that you really went out to create a world of your own. It's nice to know something so creative has gotten popular. I am sure we could all learn from this technique.

good but

i did not understand it too well but thats just me i think others may unhderstand it but i it got confuseing at the part whare the crack opens

Neat and well done

also, @Fomze: the "moral" of the story could also be 'you never know where/when you'll happiness' or 'always be aware of the world around you' or 'never take anything for granted' or, etc... you're presuming to tell everyone the moral of a story that isnt yours.

nicely done

the moral of this story is: think out of "the box"