Containers are items that are in the container category. The container items carry other different type of items. The container items also carry enemies in Versus Mode, Classic Mode, etc. The appearance of enemies out of containers is a rare occurrence though. The containers also can explode when it is destroyed but isn't a definite occurrence. To receive an item from a container, the container must be destroyed by attacks or items. Once the container is destroyed, the item inside of it will appear.
The container items also make an appearance in Super Smash Brothers Brawl. The traditional barrel and crate return as a container item, but also there are new variations of crates and barrels that varies on the stage the characters play on. For example, on the Yoshi's Island stage, the boxes and barrels are in the shape of presents. There is also a new type of item called the Sliding Box that will row down an inclined plane if a character pushes it. Container items are also now changeable via the Item Switch, however one can only toggle Container Items in general, not specific ones. The Party Ball is also now grouped in with Container Items, and doesn't have its own separate Item Switch anymore.
A list of container items: