Item Boxes are items that appear in the Mario Kart series. They contain random items which are available as the racer drives through a block, though the item depends on the racer's position in the race. Their appearance can be compared to Exclamation Blocks as they have a question mark on them. There is also a Fake Item Box that is one of the items.
In Super Mario Kart, these are called Question Blocks. They are yellow, flat panels in the road with question marks in the middle, due to technical limitations back then, limiting them to just flat panels. If one is driven over, the item list would come up, and the items will quickly scroll vertically in a roulette-like fashion; the item it stops on is the item a player can use. When a Block is hit, a weird type of harmony comes on. Its essence stays throughout the whole series.
In Mario Kart 64, the boxes are orange and blue (and now they are 3D), and are sort of diamond shaped. It is impossible to tell from a distance if a Fake Item Box is really an item box, because a Fake Item Box looks exactly the same as an item box except for a barely noticeable upside-down question mark. There are still question marks in the middle, and the boxes rotate. They must be driven through rather than over.
In Mario Kart: Super Circuit, item boxes are box-shaped, 3-D, and cycle through a rainbow palette. They rotate horizontally and make roughly the same sound when they are hit as they do in Mario Kart 64.
In Mario Kart: Double Dash!!, the item boxes are a lot different, with an alternate design and are not as much of a diamond. They are now cubes with little squares all around them. The cubes do turn like they do in Mario Kart 64, but the question marks now have a part in the animation. The question marks bounce every time the cubes turn. Also, it is now easier to distinguish Fake Item Boxes from real ones due to their red color.
Double Item BoxA Double Item Box is a feature introduced in only Mario Kart: Double Dash!!. When the player's kart collides with it, both characters will receive an item. If you've already got an item, it'll only give you one. These item boxes can show up randomly in the place of a regular Item Box, or through a special passage (e.g. Thin road in Luigi Circuit, Warp pipe in Peach Beach, etc.). These item boxes were removed in Mario Kart DS and Mario Kart Wii, as not only was the double character feature removed in those games, but one could also hold out an item to make them hold two at once. Because of the removal of the Double Item Box, all the special passages in tracks returning for the two games were also removed as well.
In Mario Kart DS, Item Boxes are practically exactly the same as they are in Double Dash!!. They appear as rainbow squares on the touch screen. Fake ones are also the same and they're represented by a red square on the touch screen.
In Mario Kart Wii, the item boxes aren't too different, except that the square pattern was changed with a circle pattern on the cubes. The cubes are still animated the same as in Double Dash!!, and the Fake Item Boxes are still red with the same design as in Double Dash!!. But what's different is that the Fake Item Boxes twirl around.
Item Boxes reappear in Mario Kart 7 and Mario Kart 8, acting the same as before. However, Fake Item Boxes do not appear in those games.