tonight show with jimmy fallon. michelle obama. michelle obama. michelle obama. reporter: her days of dancing across our screens are numbered. how cool is the first lady? reporter: cool enough to run a potato sack race in the white house with jimmy fallon. and now she s reached the finish line, it s the first lady of late night. it is nuts, i feel like crying right now and i didn t think that. reporter: her last talk show appearance featured her surprising people as they delivered farewell messages. so continue to go high, even when the challenges of life make us feel low, thank you so much. reporter: she was even sna sarenaded by stevie wonder who