Halloween is a celebration closely related to an ancient celtic festival for the end of the summer. According to some beliefs, it's also a time when ghosts and witches walk among the people...

By now very few actually celebrate its real meaning, like it has happened with most religious celebrations.

There seem to be several appointed activities for Halloween here in Johto. There will be food, costumes and candy... Also contests for carving pumpkins, so if you are in any of those towns you should be able to have the full experience.