Indeed. This was very much worth the *ahem* 5 minutes and 20 seconds it took to watch. (Meaning it's pretty long for an NG thing, so all of you low-attention-span people please go away and stop flaming.)
I'll assume that you meant for this to be an artistic submission as opposed to just a random collab. (I hope so at least) Because this was very impressive, and as a casual art admirer, I was very happy to find this on Newgrounds. I respect and often enjoy the random comedies and games that show up here, but this classy entertainment is a rare and welcome pleasure.
My favorite part was easily the rain. That scene gave it the feel of a real cardboard city instead of a city depicted in cardboard.
The music was enchanting. Very nice choice for this collab, and I congratulate whoever picked it, as well as thank them.
I wish to thank and send my respects to every single author, including Coolio for his surprisingly entertaining preloader.
Why didn't this get the max score? Well, I'm afraid to say that the ending ruined the entire mood. I literally groaned and rolled my eyes at it.
Overall, however, I wish to say this was excellently done, and that the authors should work together again sometime! =D