My cat usually wanders around the house. He'll stop by for me to pet him once, then be on his way.
But sometimes he does decide it's time for me to go to bed and be a nice little pillow, so he'll jump on top of my desk and sit down in front of the monitor.
My reaction varies from "Dear god, I hate you cat" as I'm petting and gently pushing him to a secondary table.
"Ok, ok, fine I'll go to bed, you evil little demon" as he trots down the hall after me.
And, "No, go away" as I toss him onto the sofa, leading him to go and sulk somewhere very visible in hopes I'll apologize for the great indignity.