When we were kids (she's 7 years younger than me, so she was like 3 or 4 at the time) we watched an old B horror film called Tourist Trap (with chuck connors). Parts of this movie included mannequins that had mouths that dropped open when they were fixing to kill somebody and you would hear this "aaaahhhhhhhhhhh" noise, kinda ghostly sounding.
Well for months after that, she would sneak out of her room and into mine before I went to bed and hide. Once momma had tucked me in and I was trying to go to sleep I would hear this "aaaahhhh" noise either coming from under the bed or from the closet hehehehehe It would scare me to death.
To this day sometimes one of us will pick up the phone and call the other and all we'll say is "aaaahhhhhh" and hang up.
I also had a scam going where I convinced her that any dessert she got....I always had to have the first and last bite (if my parents werent around that is)....that worked for many years until momma fixed her some dessert one day and she tried to get her to take the first bite "cause thats what shani always does)