When I was about eight years old, my friends told me an odd story.
They had recently gotten a fish tank for their birthdays. For rather inexplicable reasons, some of their fish had begun dying. They checked everything out on the fish tank (water acidity, feeding schedules, water cleanliness) and nothing was wrong. Finally, my friends told me their story - that a ghost had killed their fish.
I immediately scoffed at them, despite being a believer in ghosts. I thought that they had made it up. They were insistent, saying that a young boy wearing a baseball cap walked out of the wall and walked over to the fish tank, where he stared at the fish. Finally, he would reach in and try to touch one of the fish. The next morning the fish was dead. After hearing their story, I was fairly sure they were telling the truth and decided to spend the night.
We all stayed in the older girl's bedroom, where the fish tank was. We chattered for a while and finally were silent, waiting for him to come, which he did at about twelve-thirty. He appeared to be about eight years old, and was wearing shorts, a T-shirt and a baseball cap, which was pulled low over his face so that we couldn't see it. He walked over and watched the fish swim around in the tank. He was a whitish color and fairly transparent. We sat in silence as he reached into the tank and tried to grab a fish. We noted which one he tried to grab. Finally he left, walking back through the wall. We finally went to sleep and woke up the next morning and found the fish he had tried to grab dead. That afternoon we moved the fish tank into the living room. The fish never died of anything but natural causes after that.
I believe that the young boy must have lived in the house and possibly died there. He was not harmful or malicious, but curious about the fish they had brought in. I which I could ask if they knew anything about the history of the house or who lived there before, but they have since moved twice and probably don't remember.