This cat reminds me of my mother, waiting up for me to get home from a date.
Oh, all right -- Mom never actually sat in the window. She actually went to bed, but she never slept until we were safely home, our dates were gone, and we were far removed from the near occasion of sin. She was particularly good at sussing out when the monkey business was getting serious. So there I'd be, lounging on the living room sofa at one o'clock in the morning with my boyfriend, necking happily, and suddenly this horrific pounding would commence, like a herd of buffalo rampaging through the attic.
It was Mom, stomping around her bedroom -- sending a subtle signal to the hormonal teenagers directly beneath her that it was time to knock off the canoodling, say good-bye, lock the door safely behind the departing date, and get the hell to bed so that she could go to sleep.