My family moved into a 100 year old house about 3-4 months ago. My mom can sense spirits and stuff (hard to believe but true) and we were a little hesitent to move in but we did. Anyway, my mom just got home, went to the bathroom and when she came back out she turned the light off, then out of the blue, her and my step dad watched it turn on then off again. My exact question is, WHAT THE HECK JUST HAPPENED?? My cat is now staring in the bathroom, in the dark bathroom and I'm freeked out!

Ghosts can turn lights on and off.

Sounds like a defective light switch. And cats make it their business to stare. They sit on their haunches and stare when they aren't sleeping or eating.

They watched the switch physically move, or just the lights being on and off?

Sounds like a defective light switch. And cats make it their business to stare. They sit on their haunches and stare when they aren't sleeping or eating.
Yes mine is usually tracking a big bug that she would like for an after dinner treat

ghosts can turn lights on and off.

Only if they want to make a statement

ghosts can turn lights on and off.

So can electrical problems, which is much more likely in a 100 year old house.

I would look into electrical problems first. I suspect a worn out switch.

But I would not rule anything out until I was satisfied I knew what the electrical problem was for sure.

IF it continues that would give the "ghost" cause more reason to be investigated.

But like Alty says, it is a hundred year old house.

I wouldn't worry too much about it. You said the house is 100 years old right? You should probably have an electrician check it out just to make sure it doesn't have faulty wiring and to make sure it's not a fire hazard.