Whoopie Cushion

Two things. Click it and it plays the sound on demand. Equip it and it takes over the noise your character makes when something hits you, which is either the funniest thing in your world or something you remove within the hour. It gives no stats, so put it in a social slot where it costs you nothing and still works. If you ever hear the noise without owning one, it is the Companion Cube pet, which shares it.

Giant Worms and Diggers drop them underground and deeper, so any long mining trip turns one up eventually without you trying. If you would rather not wait on the roll, throwing a Zombie Arm into Shimmer converts it into one directly, and zombie arms are easy to come by on any ordinary night. It cannot be reforged, so there is no modifier to fish for.

It is an ingredient in things that are not jokes. The Fart in a Jar is a genuine double jump and one of the earliest mobility upgrades you can put together, and it needs a cushion. Later the same item goes into the Fart Kart if you want the mount. Shimmer runs the other direction as well, turning a cushion into a Gas Trap for a build. Hang onto the first one that drops instead of selling it.