Shadows
Once every year, always around October, Jenkins was very busy.
The first year the LITs were working in the Library and it happened, Cassandra believed it to be a poltergeist, because it occurred in all of the rooms in a really creepy way, complete with flickers and, after that, with total darkness.
This was the month most of the lamps in the Library started to burn out and Jenkins had to replace them. He worked methodically, from one room to the next, careful not to forget even one small bulb.
He knew that shadows in a Library could get dangerous...
A/N: Any Whovians around? Otherwise... this is probably not that funny :D
By the way: I spent a year working at a Library and can tell you that really all of the bulbs burned out at the same time. I had just started the first series of 'Supernatural', so I was looking out carefully for any poltergeist-signs... :D