DBF's cat doesn't like closed doors. This includes bathroom doors. He'll come in and stare. I inevitably hear DBF saying something like "Dammit, cat, I don't stare at you while you're on your litterbox!" He also insists on staring while the bathroom occupant is taking a shower.
I just tell DBF that at least the cat doesn't look up and go "Ooh, dangly things!" with claws out...