The president struck a pose during a photo op at the reception, and the pose stuck -- for about 130 pictures.
Check out the montage below created by Eric Spiegelman to see how Obama's face doesn't seem to change for any of the photos. It's kinda creepy.
When someone yells "Cheese!" Obama apparently takes it seriously. His cheeks have to hurt after holding a pose for that long.
Maybe there's some sort of official smiling czar in Obama's Cabinet that we don't know about...