Mumbo Crates are small pink boxes found scattered in various locations across Showdown Town in Banjo-Kazooie: Nuts & Bolts. They are indentified by Mumbo's skull on the side of them. When found, Banjo must drive them back to a small pink area outside of Mumbo's Motors to get Mumbo to open them. The crates contain parts for use with your in-game vehicles. Some items found in crates are rare, and are usually inside of the harder-to-find crates.
Stop 'N' Swop Crates
Stop 'N' Swop Crates are a special type of Mumbo Crate found when you collect the appropriate Stop 'n' Swop items in the Xbox Live Arcade version of Banjo-Kazooie. Nuts and Bolts will then recognize that you have found the items and place a Stop 'N' Swop crate in Showdown Town. The crates are colored according to the item found and contain special novelty parts (Fuzzy Dice, for example). The are only one of each of these items in the game (excluding however, the flag, as you get 2 in the box). While the game does show the location of the crates after collecting the item in Banjo-Kazooie, these crates are usually harder to find and require some thought.