Pumpkaboo is a ghostly pumpkin-like Pokémon that varies dramatically in 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 in its body. However, its own spirit is trapped in this world. Pumpkaboo can hypnotize and control any humans or Pokémon. It does this task by releasing streams of light from the holes in the pumpkin.
Pumpkaboo has four separate forms: Small Size, Average Size, Large Size, and Super Size.
The size of Pumpkaboo is said to be the product of the number of lost souls that lingered in the area where it was formed. When taking spirits to the afterlife, small Pumpkaboo prefer the spirits of children to those of adults. Supersized Pumpkaboo are very partial to the spirits of people who were of similarly superior proportions.
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.
Pumpkaboo have four different forms, each named after their respective size: Small Size, Average Size, Large Size, and Super Size.
Its size is maintained through evolution into Gourgeist and cannot be changed. Larger sizes of Pumpkaboo are rarer to encounter in the wild. Bred Pumpkaboo are the same size as their mother, or the same size as the Pumpkaboo or Gourgeist parent if bred with Ditto.
In the wild, Super Size Pumpkaboo will always hold a Miracle Seed, whereas other sizes will never hold an item in the wild. Super Size variants have different, lower-pitched cries than the other forms, and were also the only Pokémon to have the XXL size designation in Pokémon GO prior to the addition of XXL and XXS sizes for all species. The different sizes of Pumpkaboo do not use different menu sprites, except in Pokémon HOME.
Each form has different base stats. With each increase in size, Pumpkaboo's base HP stat increases by 5 points, while its base Speed stat decreases by 5 points. Consequently, its base stat total does not vary with size.
Pumpkaboo appears to be 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).