There are two possible sizes of Pumpkaboo available at the Beryl Cemetery, Small and Super Size. These appear to be the only sizes available in the game, as these are the only ones listed in the montext file. Either one can appear from any of the large pumpkins. There is a distinct difference between their sprites and cries, with the Small size having a lower cry, and the Super Size having a rounder bottom between its legs (Small size has a flat line between its legs). For anyone curious, I've also verified that both sizes have a 5% chance to be carrying a Miracle Seed.