Cubes are transparent containers that appear in The Subspace Emissary. There are two varieties of these cubes, both of which can be opened when attacked to release items. In some levels, cubes can appear in midair and can be stood on until broken, which may help in rooms with falling platforms.
Turquoise cubes appear every time the player enters an area. They may contain items, collectibles, healing items, or Stock Balls. Any single cube in a level will always contain the same type of items each time, but the specific item(s) inside may vary. For example, a given turquoise cube may always release shooting items, but different ones each time. When a turquoise cube is set to contain healing items, it may have multiple varieties of food (including a Party Ball), two Maxim Tomatoes, or two Heart Containers. The quality of the item(s) found depends on the difficulty level, stickers attached to the character, and whether continues have been used while playing.
Orange cubes appear in a level only until the player breaks it for the first time, after which it will stop appearing. Orange cubes only contain collectible items like trophies, and increase the Clear % when broken. They typically are tucked away in hidden rooms or alcoves. For an orange cube to count, it not only has to be broken, but the contents inside must be collected.
On the world map, a stage where not all orange cubes have been collected yet will be marked with a flag. This will change to a flashing crown once all orange cube items are collected along with any hidden doors or other requirements. Finding and opening every orange cube is required to get a 100% clear.