Our ghost used to turn Pcs on.
I got a call from some medical but non technical people.
We asked users to log out of computers at night but not turn them off so that we could scan, update etc all of them. Thery had discussed it amongst themselves and concluded that we couldn't possibly mean that and carefully turned off the computer and left the screen on. This was in the days before "magic packets" so i set the BIOS to turn it on at 06.00 on weekdays.
We got a call that a "ghost hacker" was using their computer every night. When the story got out, some of our consultants took to unplugging their computers at night and calling us up in the mornings because they were slow!