I used to believe that there were very scary things hiding just outside my peripheral vision. They're always behind me, and move fast enough to avoid my sight when I turn around. Like vampires, I wouldn't see them in the mirror, either.
I wasn't yet into computer gaming at the time, but it's very similar to Star Control 2's (early 90s) alien Spathi and their fear of the Ultimate Evil, which "lurks just outside the range of even the most sensitive, long-range detectors". Eerie.
A childhood belief about vampires

others believed things like this
- As a child I believed that when a person was fired from their job, they were executed on a firing range. — damien
- My sister thought a fruit machine (the gaming device) could turn one item of fruit into another.— Richard Davies
- I had a fear of seeing a person in the corner of the mirror(most of the time a morlock)— Shane
- I used to believe that the remote control could control all the things in my house, including my dog.— Felipe
- I used to believe that my reflection in the mirror was my evil twin that always had bad hair. XDAnon
- I used to believe that when people die, they turn into a star.— Allan