Pop star Lady Gaga performed on "The Oprah Winfrey Show" - a day after calling off a concert at Purdue University because of an undisclosed illness. The singer showed no apparent signs of illness as she performed a medley of her hits on the live show Friday. She wore a black outfit studded with spikes and, at one point, swung a gold, spiked ball on a chain into the windshield of a taxi on the stage. The concert cancellation was announced from the stage Thursday night after opening acts Jason Derulo and Semi Precious Weapons had already performed. A statement released by the school from Lady Gaga`s tour management said she`d suffered a sudden illness and that medical personnel had advised her not to perform. The concert was rescheduled for Jan. 26.