system
A chat on 4chan
human
I grew up in a haunted house with a very active poltergeist. Mostly harmless but prone to mood swings. We moved out when I was 10 & my sister was 14 because it suddenly got violent & dangerous (throwing knives). I've heard since then from many sources that girls in puberty make ghosts go crazy... But you wanted benign stories, so here's a very common occurrence;
>be me
>little kid
>innahouse alone
>mum doing gardening 
>dad fixing POS 1970s BL car again
>sister out at friend's house
>be watching cartoons
>want cereal
>go to kitchen for cereal
>big house is big, 4 doors between sitting room & kitchen
>go through door from sitting room to hall
>SLAM door slams shut behind me
>go through door from hall to dining room
>SLAM door slams shut behind me
>go through door from dining room to smaller hallway
>SLAM door slams shut behind me
>go through door from smaller hallway to kitchen
>SLAM door slams shut behind me
>giggle and say to ghost 'Haha Charlie that was fun!'
>I called him Charlie all the time
>dunno his real name
>make cereal
>toomuchmilk.bmp
>have to focus while carrying it to not spill
>say to ghost 'Charlie can you do the doors again?'
>ghost opens kitchen door
>I walk through 
>SLAMS it behind me
>repeat with other 3 doors, same thing
>get to sitting room
>say 'thanks Charlie!'
This was a very common, almost daily thing. If he was in a good mood he'd open them for you & slam them behind you, when he was in a bad mood he'd slam them in your face.
When I was little I thought ghosts were normal, since I'd only known life with one around. I used to talk to him when he was in the room like he was just another family member, never saw an apparition of him, never heard him speak, but he could move things around, open & shut doors, drawers etc, thump/bang on the walls (like he was punching them) and we'd hear his footsteps pretty much every day. 
TL;DR I had a ghost friend as a kid.
gpt
kinda sounds like a tulpa too. cool.