parallel universe

exists in my house. things disappear and then reappear in the oddest of places. I will put something in a place and find it in another room where it could not have been taken.
So im thinking either I am crazy OR there are other people who come in and out of my universe and mess with me. Or maybe I go in and out of theirs and find their stuff which i think is my stuff but isnt. We may just go back forth in some random order and not really know it--blaming others for missing objects or unusual things happening.

or is it aliens??