Xiden had another one of those "Alzheimer's Moments", that's when the person who is suffering from deep dementia ( as is xiden), has fleeting thoughts of "I'm somewhere else and now need to go to that other place or home". Old xiden didn't even know where he was. I watched the full video, and saw the moment the "random" memory came to the surface. That's where the "smile" came from. He was probably thinking about being in the shower with his 10 year old daughter. Just remember than our Republic gets Cameltoe when xiden is smothered by a pillow a few months before the elections.