I Ace and collect all of the single-player Goodies in the "The Darkness" level.
I tend to loathe levels in which the player has to navigate in obfuscating dark, but I find that I actually quite like this level. I think it's really well done.
Revisit: No revisit is mandatory, but I separated the Cooperative Challenge areas from the collection of single-player Prize Bubbles to make it easier on myself.
This video covers the Cooperative Challenges (and their exclusive Goodies) in the "The Darkness" level. I consider the first Challenge covered in this video one of the harder ones in the game, but at the same time I also think it is one of the most fun. Unlike a number of other Challenges in which one or more of the players hold down a Button or do some other boring and simple task, this Challenge requires the combined effort and teamwork of at least two people.
While I screw it up in the video, it is possible to do a safe exit of the first Challenge area. The player(s) on the lower area can use the stone blocks to jump up to the end of the upper area. Then, all the players can use the rolling light to safely travel back to the beginning of the area.
Viewers are likely to notice the alarm sound during the successful run of the first Challenge area. In case you're curious, that signifies that we were on our last life and that there would be no more respawns from that Checkpoint. Furthermore, we had already used up all of the extra lives from the Checkpoint at the beginning of the Challenge area. We resorted to using the Checkpoint near Don Lu and below the Challenge area in order to give us a few more attempts. The alarm signifies that we had just exhausted that second Checkpoint right before the successful run.
There are a few ways to pick up the colored Piñata Motif Stickers. The easiest way is to have the player controlling the rolling light to drop down onto the floating Prize Bubbles. I managed to pick up the Red Piñata Motif Sticker with a high jump, but I think I just got a very lucky boost from the edge of the spiked block. (Maybe I inadvertently performed a lucky corner jump off of it?) Also, if you play this Challenge area with four players, three (one below the other below another) can dangle off the rolling light so that the bottommost player will collide with the Prize Bubbles as the roller is moved. Dropping down is the easiest, but choose whatever works for you.
Special thanks goes to the random online player featured in this video. The other player (the one without the tuxedo, who seems to be wearing a box, a white ruff, glasses and a turban) goes by the PSN ID of Rainlulu. She was a real trooper during this level, and I really appreciated her help.
Note: The New Items screen shows that I only got +2 New Items (instead of the reality of +8) because the two of us managed to exhaust all of our lives before making it to the end of the level in one playthrough. Thus, we retried the level from the beginning, completed the second Cooperative Challenge area and only then did we successfully make it to the Scoreboard.