[Billy's in the middle of his getting-ready-for-bed stage of the day, since there isn't as much to keep him awake late at night as there was back home. He's only half-dressed and brushing his teeth when the door knocks, so Susan will probably here a hasty thump-thump-thump of his feet as he scrambles to get a shirt on, opening the door a moment later with frumpy hair and a toothbrush in his mouth. Whoops, he'd forgotten she was coming back.]
[action]
...Mmrrow.