Halloween is a time of year when the barrier between worlds weakens. Spirits and youkai have long taken advantage of this fact, and in this modern, computerized age, digimon have begun to do so as well. It started with Bakemon, veterans of Vamdemon's 1999 invasion, for whom Halloween was equal parts nostalgia trip and scare-fest; they passed unnoticed for a while, until the locals realized the 'costumes' came with no legs, yet were still moving, chasing them, and occasionally grabbing them with mysterious blue hands.
These encounters set the tone for future digimon Halloween celebrations; none of the malice of the actual invasions, but pranksters from the digital world could do a number on the usual holiday experience. Haunted houses become far more terrifying when a Deltamon chases children onto the street, while Candlemon's habit of lighting jack-o-lanterns often overworked local fire departments.
Despite the frequent disruptions in other parts of Tokyo, Shibuya's famous Halloween parades have thus far passed without incident. Credit for this belongs to what were once believed to be two small children, wearing full-body costumes – a pumpkin with an axe in its head, and a statue made of rocks. But those in the know long noted that only one of them, properly speaking, was even a Child at all, and as the years went on, neither grew even an inch, and the world came to learn what digimon were.
Other digimon have learned the hard way to give these two a wide berth, and not to terrorize people in Shibuya. This is an honor these two once reserved to themselves, but as they learned more about human culture, Pumpmon and Gotsumon have evolved into the role of protectors. They are happy to show digimon tourists around Shibuya, but unforgiving of antics like ice cream theft and jumping on traffic lights, at least (they have let it be known across Overdell, to avoid charges of hypocrisy) if they take place on Halloween. In 2013, the two were granted the honorary position of parade marshals – the first digimon so honored in all of Japan, and perhaps their real motivation for protecting the parades.
Shibuya's parades have only grown more popular (among whole families, not solely young adults) in response to the chaos in the rest of Tokyo, which the Chosen Children struggle mightily every year to contain. At the same time, adolescent humans who value adventure more than candy or parties have taken to trick-or-treating in the digital world, despite the… considerably variable quality of the treats.