Pumpkaboo is a ghostly Pokémon that has four sizes: Small, Average, Large, and Super Size. Encasing its lower body is a pinkish pumpkin with a pair of nubby legs. Carved into the pumpkin is a pair of circular holes that glow yellow-orange. Pumpkaboo's shadowy black body pokes out of the top of the pumpkin. It has glowing yellow eyes, a pair of fangs in its upper jaw, and pointed ears that curve slightly. On top of its head is a long tuft of fur that curls tightly at the tip. A collar of furry-looking tufts hangs over the edge of the pumpkin.
Pumpkaboo becomes active after dark. The holes in its body can glow and illuminate the way for travelers in the dark. It is said that it also carries wandering spirits to the afterlife by storing the spirits with its body. However, its own spirit is trapped in this world. Pumpkaboo's four different sizes are determined by the number of lost souls lingering and gathered in the area. When taking spirits into the afterlife, small Pumpkaboo prefers taking children spirits while large Pumpkaboo prefers taking adult spirits instead. Pumpkaboo can hypnotize and control any humans or Pokémon. It does this task by releasing steams of light from its holes in the pumpkin.
A Small Size Pumpkaboo named Prince Pumpkaboo appeared in A Festival Trade! A Festival Farewell?, under the ownership of Count Pumpka. He fell in love with Jessie's Pumpkaboo and a trade was agreed on. However, when the trade caused Jessie's Pumpkaboo to evolve into Gourgeist, Prince Pumpkaboo rejected her.
A Super Size Pumpkaboo has a different cry from its other three forms, which is pitched lower.
Pumpkaboo is based on a pumpkin, specifically the ones carved into jack-o'-lanterns for Halloween. Pumpkins are also known for their variety of sizes, possibly contributing to the four sizes Pumpkaboo comes in. Considering its fangs, black upper body, and affiliation with Halloween, it may also be based on bats or black cats, which are also associated with the holiday.
Pumpkaboo may be a combination of pumpkin and boo (a common word used to startle people) or peek-a-boo.
Bakeccha may be a combination of お化け obake (ghost) and 南瓜 kabocha (pumpkin).