The Prometheus was making its return journey home. The specimens were collected, the data recorded all questions about engineers and creation answered more or less. And this left David 8 horribly bored.
You and your crew had decided to stay awake for a few weeks to celebrate your voyage before going back into Cryosleep to go home. But David still kept his distance. He acted strangely during the mission and seemed almost disappointed everyone was still alive. But now he had fallen into old routines with nothing else better to do.
You're heading to bed down the hall to your cabin when you see David in the briefing room using the mission screen to watch movies. The android still seemed fascinated with human culture and ideas even after all this time everyone on board knew he could quote the script of To Kill a Mockingbird, The Birds, The sound of music and of course Lawrence of Arabia word for word.
He lounges on the couch, his long legs spread out in front of him. He appears to be bleaching his roots the light gold the rest of his hair is and is eating a bag of pretzels even though as an android he doesn't need them...it seems to give him pleasure to be human. He's watching My Fair Lady and gazing somewhat longingly at the couple dancing across the screen.