Pumpkaboo is a ghostly Pokémon that resembles a pumpkin carved into a jack-o-lantern. The top part of its plump, round pumpkin-like body is covered in a thick shag of brown hair that curls upward slightly at the ends. It has a curled stem at the top of its head, and two horn-shaped tufts of hair on either side. It has two ovular yellow eyes and a small mouth with two sharp fangs protruding from beneath its upper lip. The bottom part of Pumpkaboo's body is orange and pudgy, with two short legs and two holes that seem to have been carved out. Inside Pumpkaboo's body, a mysterious orange light can be seen.
Pumpkaboo come in various sizes, ranging from small to super-size. The size of a Pumpkaboo determines its stats.
Pumpkaboo and Gourgeist are the first Pokémon in the games that may have different sizes.
Pumpkaboo's HP stat increases by five (44 small, 49 average, 54 medium and 59 large) as its size increases. However, its speed decreases by five as its size increases (56 small, 51 average, 46 medium and 41 large).