When I was young (6? 7, maybe?), my friends and I were convinced that spirits (good and bad) could become trapped within the grain of wood in furniture and paneling. I truly believed that an evil spirit named Willy resided in the dimly lit back corner of the wood-paneled dining room in my house. I would have nightmares about Willy coming out of the woodwork (literally), grabbing me in my bed, and then trying to drag me into the dining room and into the wall with him. The dining room was safe in the daytime (thanks to the two large windows that brightened it up significantly) or even at night as long as an adult was there, but I was probably 12 before I could bring myself to go into the dining room by myself after dark, even if the overhead light was on in the room.
A childhood belief about monsters

others believed things like this
- i used to believe that a ghost lived under my bed and that a giant lived under our dining room table.— nameless
- i believed that if you farted too much in a room and you were to light a flame your house would blow up— the nuclear fart
- I used to believe the living room furniture would party after we all went to sleep.— Ellen
- I believed that the pictures on my nighties came alive at night and played in my room while i was asleep!!Anon
- When i was younger, i used to believe that the hanger in my room became a witch every night.— Laura
- When I was very young, I believed that houses were carved out of one gigantic block of wood.— tinmanjones