Broer & Zus (1999)

The episode Pieter and Anders from the series Broer en Zus is about two timid brothers, identical twins, who are withdrawn into a world of their own making. There they flourish. This world is filled with living skeletons, that throw all your household effects to smithereens if they feel like it. Two aging Father Christmases watch sceptically and think their own thoughts. Are these the alter-egos of Pieter and Anders?