Black Boo

Black Boo is a type of Boo found only in Super Mario Bros. Deluxe. In You vs. Boo mode of the game, Mario will encounter Black Boo as an opponent to race. After Mario competes and wins against Red Boo enough times, the Red Boo will forfeit, and Black Boo will enter the competition. Black Boo is the quickest Boo in the game and will speed up most of the time, making it the hardest opponent. Mario must defeat it a number of times to clear the You Vs. Boo mode.

Interestingly, the Bomb Boo from Super Mario Galaxy resembles the Black Boo.