Boo Pipes

The Boo Pipes is King Boo's unlockable kart in Mario Kart: Double Dash!!. It is a gray version of Petey Piranha's Piranha Pipes, and can be unlocked by completing the Special Cup in Mirror Mode.

Unlike most heavyweight karts, the Boo Pipes is unique for having traits similar to that of a lightweight kart; low top speed and high acceleration. But unlike the lightweight karts, this kart is heavy enough to rival the weight of the Koopa King and Piranha Pipes. These traits make the Boo Pipes a very effective kart to use in GP races. However, it's not very useful in Time Trials, due to its low top speed.

Although it has a four star acceleration stat, the Boo Pipes actually accelerates slightly better than the Goo-Goo Buggy, which has a five star acceleration stat. Oddly enough, even though it has a two star speed stat, it is slower than the other two star speed karts, and its speed is really tied with the Goo Goo Buggy and the Koopa Dasher.

It is one of the four "out of the ordinary" karts for its weight class, with the others being the Green Fire, the Turbo Birdo and the Barrel Train.

Trivia

 * In terms of stats, the Boo Pipes may have been designed to be a heavier version of the Heart Coach, a medium kart with near-identical stats (other than weight) and even the same engine sound.