I Ace and collect all of the single-player Goodies in the "Great Magician's Palace" level. While this level is the most difficult of the "The Temples" area, comparatively it's still not as bad as some other levels. Most of the difficulty here has to do with timed platforming (which is simple once learned) rather than precision or defeating enemies and so on. The three column block-dropping part tends to trip up a lot of people (including me in my initial playthroughs) and seems a lot more difficult than it actually is. There is a repeating pattern to the block-dropping, and once you know what it is for that attempt, it is easy to time your jumps in such a way that enables you to succeed with your one chance to get it right.
I've always thought that this level was one of the most technically impressive levels of the entire game. Its aesthetics are nice too, but it uses Emitters to fantastic effect.
Revisit: No revisit is mandatory, but I separated the Cooperative Challenge area from the collection of single-player Prize Bubbles to make it easier on myself.
This video covers the Cooperative Challenge (and its exclusive Goodies) in the "Great Magician's Palace" level.
Special thanks goes to the YouTube volunteer featured in this video (he is the default Brown Knit Sackboy holding a Mini Sackboy doll). His YouTube account is Spongebob1212X and his PSN ID is SpongebobFTW1. Special thanks also goes to the two random online players featured in this video. Because they were dressed up so similarly, I honestly can't remember which was which. Nonetheless, one of the random online males goes by the PSN ID of partridgepride. The other, for whatever strange reason, had his display name as a string of question marks. I assumed it was a glitch and that I never got to see his real username while we played together, but maybe he actually chose a bunch of question marks as a display name.