The Wedding Reception

You can't miss the 8 Costumes near the very beginning. After passing through the skeleton, knock over a series of vertical platforms to find 3 Materials and an Object. When you reach the board held in place by two-springs, bounce off of it several times to get enough height to reach an Object high above, a Material to either side, and finally onto a platform on the right where you'll find a Sticker Spot. Plant a Skeleton Hat sticker there to reveal two decorations. Afterward, you'll spot an Object on a platform in the next gap.

At the first balloon section, grab hold of them to catch a ride to the platforms above, where you'll find 6 Stickers and an Object. Just after, you'll find several egg-shaped objects attached to Bungee cords: grab the left-most one and lower your into a secret room, halfway up the left wall where you'll find four Objects.

Ride the balloons up to some hidden items.

The next room contains several bubbles surrounding a skull-like mural in the background. You're going to have to grab the stretchy-string in the center, then use it to bounce into the spring below, allowing you to grab them. All in all, you'll collect an Object, Sticker, and 3 Materials. If you're playing co-op, Skip the skull just ahead for now and continue into the next room (Requires 2 Sack Boys)

Bounce off the subsequent Skull to reach a ledge above. Now look at the center skull-notice something missing? Plant the Huge Eye sticker on his missing eye to reveal a Costume. Now head to the far right and drop to the level below, grabbing hold of the roller along the wall to dislodge an Object. The room just after (to the right) contains several goodies you can grab, if you have two players:

Return to the area above (by the skull that was missing an eye), then bounce off another skull to the far-right to reach an Object on a platform to the left, then continue upward by landing on the right ledge. You'll find a series of skull lifts that'll bring you up to a checkpoint--jump off of the far-left lift once it gets close to the top to jump onto its head and grab an Object. Now jump to the platform to the right, and cross over the tops of the skulls for four decorations.

When you reach a series of hanging springboards, drop to some skull-platforms below and look for a secret tunnel on the left, where you'll find 5 Stickers. Now return to the spring boards and use high-bounces to reach a Decoration above each one (5 total!). Shortly after crossing a bridge with a large skeleton in the background, you'll come across a shaft with several skulls--bounce off of them to grab an Object halfway up the shaft, two more above it, then 3 Stickers on the left ledge. From here, leap onto the skeleton's hat to the left for an Object, Audio Object, and a Key.