The Blink episode of Dr. Who scared the crap out of me. It featured these aliens/monsters, Weeping Angels. They freeze in place (as stone statues) when they're being observed, but if you blink or look away, they quickly and silently move... towards you. o.O
There's even a Minecraft mod featuring them. I had a REALLY hard time watching this Yogscast video.
I think Lucy is part Weeping Angel. I'll be in the kitchen making dinner or washing up with no sign of the elusive kitten. But then I'll turn around and there she is. Silent and immobile. Just staring. Look away for a moment and look back - she's inched her way closer. Still staring.
So I laughed and said "Hey James, I think Lucy is a Weeping Angel..." Then I stopped laughing.
And now I'm scared of my own kitten.
[Update: And I thought Lucy was creepy. This cat takes the cake.]