your dreams are actually about 65% influenced by what you see and think before falling asleep, and sound can affect it when you are sleeping. for some reason, if you are asleep, during a tv show, if you hear it, your dream seems to create an awkward storyline that goes with the sound but dosen't make much sense. and, for some reason, all events seem tied together. also you can control dreams by simply imagining something happening, although i've never done it because usually i don't realize i'm dreaming.
tl;dr- don't think about or see scary crap before sleeping.