Sister's Desktop Fan is a gadget in The Bigg House, found after completing all quests in the Sister's Bedroom. It is a foot-tall (roughly 4 inches when shrunk) fan that is black with pink and white words and designs on it.
Like most gadgets, the fan has three functions. The first is to blow out fires and fog/smoke that blocks your path, which will allow you access past it. Secondly, when venturing into water-filled areas (like the pool, aquarium, flooded basement, and bathtub), you can aim the fan at a section of water, and after a few seconds it will create a small iceberg that you can jump on as a platform. The third is as a tool used in platforming, which will help you glide and hover. Some areas of the house can only be reached by hovering with the fan.