Three-person percussion instrument native to the Whos of Whoville, from the 1966 Dr. Seuss animated television special How the Grinch Stole Christmas!
A kettle drum and bass drum (square so it doesn't fall off) are mounted on a long, low wheeled platform resembling a giant skateboard. A likely optional third Who, seated at the rear, plays a portable tubular bell or chime. Possibly an instrument primarily for children, based on its size.
The instrument is not in the original 1957 book.