I came home from classes one day and walked to the back door to get the dog food to feed said dogs. It should be noted the stairs to the basement was directly across from the back door. I suddenly heard three loud thumps coming up the stairs, so I think my sister must have come home early, that basketball practice must have been canceled. So I open the door and hear steps run back down and I catch a small girl with long blond hair run to the left. I yell my sister's name a couple times without any response, then finally yell, "Dammit answer me!" when I realize my sister isn't home. No one is home except for me and my two dogs, who were outside, and I saw a girl who wasn't real.
Fast forward a couple months, and I'm with my then boyfriend at his house when I get a phone call from my sister who is in hysterics (and also does NOT believe in ghosts in the least). I try to calm her down, ask what's wrong. She said she was home alone downstairs working on her senior project when she hears typing from the computer room. She looks up to hear the typing stop, so she thinks it must be her imagination. She goes back to work when she hears the typing start up again, but stops when she looks to the room for a second time. She thinks one of the dogs must be hitting something so as she's about to call the dogs over to her she sees our black lab run over to her with his tail between his legs like he's scared. She remembers me telling her that room is haunted, but she's always brushed me off about it, but the sudden thought starts to worry her a bit. She tries to ignore the sound, believing it will stop if she pays it no attention. The typing starts to get more aggressive with papers from the printer slowly falling out onto the floor. She's starting to freak out but is also trying to find some logical solution to it. As she's about to go in the room to investigate to debunk whatever it is, a thick stack slides out of the printer and drops with a thud to the ground. Needless to say she took her shit and booked it upstairs yelling at our dogs to come with her. She grabbed her phone to call me, already about to have a breakdown when she hears it. She hears three loud thumps come up the stairs and stop. Then shortly after they ran back down. That's when she called me crying and demanding I rush back home. It creeps me out to this day to retell that story - but also a small part of me still thinks, "I told you there was some scary shit down there, but you just had to tease me until it nearly made you pee your pants!"
Edit: a word and a couple spelling errors