In Mario Kart: Double Dash‼,only Mario, King Boo and Petey Piranha can get the red fireball, Luigi is the only character that can get the green fireballs. When these guys throw this item, it will split into 7 different flames, and bounce all over the place! If you get hit, your character will be faning their backside, and anyone can easily punch you. You can get these in first place, meaning that they aren't that helpful. However they are pretty powerful, they will make a Bowser Shell go crazy if the fireball hits one.
Mario Kart 7
In this game fireballs come out of a new item the Fire Flower. Unlike the first appearance of this item they only come in red and any player can use it.