A boy moves into a new house and is convinced that there's a monster under his bed. The monster under the bed is certain that there's a boy above his bed. Both call for their mothers over and over, but the mothers don't see anyone. The boy and the monster start crying, because they're afraid. They stop crying after hearing the other and slowly look above and below the bed. They share that their mothers think that boys/monsters don't exist. Then they swap beds and call for their moms.
Why I recommend it: The ending is such a twist on the usual storyline. The mothers are patient almost to the end.