A few years ago I had a tabby cat named Tiger. He was a pretty healthy cat, and then one day he became ill. My mother and I took Tiger to the vet to see what was wrong with him, and the vet took Tiger into a back room to check him over. My mother wanted to go back into the room so that the cat wouldn't freak out (since he was kind of old we worried about him having a heart attack or something if he got too freaked out), but the vet said no.
We waited in the waiting room for about 10 minutes, and then the vet came back out and told us that Tiger had died of cardiac arrest.
We put Tiger's body into his carrier, took him home, and buried him in the back yard.
That night, I was up in my room mourning for Tiger, my mother was up in her room, and my uncle (who was visiting) was downstairs. My other two cats were downstairs. I didn't own any other animals at the time, and there was no one else in the house. Anyway, all of a sudden, I heard something run very hard and very fast down the stairs. Now with Tiger, he was the fastest of my three cats, and whenever I'd open a can of cat food he would always run very hard and very fast down the stairs to get to the cat food first. Whatever ran down the stairs sounded exactly like Tiger. I guess I wasn't the only one who heard the noise, because I heard my mother yell "What's that?", and my uncle came to the foot of the stairs and said "Gwen, was that you?" I said "No!" Then he said "Sis, was that you?" My mother said "No, it wasn't!" Then I heard my uncle go, "Oh...okay..." and he went back to the T.V. room to watch T.V.
The noise came back a week later when I was home alone. I was downstairs in the T.V. room petting my two other cats who were cuddled up in the chair with me, and I heard whatever it was run down the stairs again. I quickly picked the cats up off of me and put them into the chair, and then I ran out to the hallway. There was nothing in the hallway. I would also hear little meows now and then when I was alone, and something would scratch at the back door. I would always check, and there would be nothing there. After a few weeks all of the strange noises stopped. My mother and I eventually moved to another city. I don't know if the new owner hears anything.