One time I slept over at my friend's house, and she told me that once she slept over at another girl's house and they were telling scary ghost stories and she told her that when she knocks her bedroom wall, someone knocks back. they knocked on the wall to check if it's true. suddenly someone knocked back. they were amused thinking it was the people next door or something. then they realized the oter side of the wall doesnt face the other appartment, but into the boiler room that locked shut for years.
some other weird stuff happend to them that night, the huose door that was locked opend by itself, they were pretty scared.
From all the things she told me, the knocking thing really got to me, I thought it sounded worth checking and when I got back home I knocked the wall three times.
Nothing happened. I felt so silly thinking something would!
10 minutes later while im already in bed, suddenly, from the silence I heard three slow knocks from the other side of the wall. I got upset and left the room for a few hours.
Some time later me and my boyfriend were sitting together on my bed, leaning our backs on the wall, and I told him the knocking thing.
he is like the most scepticle guy ever and he convinced me that I was probably dreaming or that it was not from inside the wall. I got convinced and we both smiled and laughed (with reliefe) and he just sorta knocked the wall behind him twice to make fun of the whole thing. we were just kinda about to cuddle when in a matter of second came two, loud, slow, knocks..
we looked at the wall, then at each other, then back at the wall, and then he grabbed my arms and warned me "don't ever ever touch that wall again sweety, ok? EVER!"
so yeah that was another weird thing that happend in this house..