At my museum, I have two interns from HS.
Now, full disclosure, I informed them on their respective first days of work, that the building we're in *used* to be a furniture store and mortuary in the 1930s and before that had been a car parts store, with a Masonic lodge hidden in the upstairs. The basement is where all of our non-display non-paper items are stored, still looks VERY much like a mortuary, including the pit where they would drain the corpses. Also, being a museum, we have 1 1/2 full human skeletons in boxes in said basement (I have not disclosed that one of said skeletons was a mass murderer), and an assortment of fossils and bones of various creatures. I told them this on their first day because the situation may come up where they would be required to handle these objects and operate in this area, and I wanted to make sure they didn't have any misgivings. Both said they had overactive imaginations, but could probably hack it just fine.
Well, needless to say, the two of them became friends, but work different hours, and so they will consistently up the ante on each other regarding creepy happenings in the basement.
First one reported hearing speech, then the next reported seeing things in the dark, and then while I was upstairs doing things one of them called my cell phone and asked me to come down right away - she sounded pretty upset. So, I took the elevator from 2 to basement, and found her standing there trying to call it down pretty frantically, and after the shock of me being in the elevator wore off, she informed me that there was a pile of dust on the floor in the draining room that had children's shoe prints in it and she was done being in the basement for a while. So, I sent her up and went to investigate.
Indeed, right in the best lit spot, was a small pile of dust, with two children's shoe prints carefully put into it to look like they were stepping.
Could it be spooky ghosties? Probably not I'm inclined to think, but I know that *I* didn't go through all the trouble of finding kid's shoes, sweeping up a bit of dust, and then carefully pressing them into said dust in a walking pattern, so now I'm on the search for the prankster.