The Mene Hene will steal your things unless you clean your room.
In order to get the subject to clean her room, her mother would tell her that the Mene Hene, (well known elfish beings in Hawaiian culture) would steal her things. The subject describes the Mene Hene as thievish little elves. To the subject, the story of the Mene Hene was her mothers attempt to motivate the subject to not only clean her room, at any given point, but to also continue to keep her room clean for fear she would not be able to find her things (clothes, shoes, toys, etc.) when they were needed. Furthermore, it is important to note that the story of the Mene Hene was only told to her while her family still lived in Oahu, Hawaii.
I am sure if one were to look in other cultures they would find that there are many variations of this same saying. The creatures/ beings that will steal your things might be different but the effect is the same.