West Wing, The Easter Egg - Mark Harmon Cameo

During the scene where Bartlet's staff is eating dinner outside and singing a song, if you look in the upper left portion of your screen, you will see a man with an apron wearing a green shirt. He is cooking something on a grill. This person is actor Mark Harmon. Harmon's character, Simon Donovan, was killed in the season three finale of West Wing.