Oprah Winfrey says goodbye this week. Tune in Monday for Part 1 of the star-studded surprise event that includes performances by Beyoncé, Usher, Aretha Franklin, Patti Labelle and Alicia Keys. Part 2 airs Tuesday. On Wednesday, the finale episode of the 25-year series airs. On Thursday, head over to OWN to watch the afterparty special on the "Gayle King Show."