Oprah Winfrey walked on stage at Chicago's United Center on Tuesday night to receive a standing ovation from thousands of her fans and greetings from Tom Hanks, Tom Cruise and Madonna.

"You always had the power, and that is the message you brought into our lives," Cruise told Winfrey.

Hanks told her that her fans just wanted to say thank you "for what `The Oprah Winfrey Show' has meant in our lives." Winfrey announced in November 2009 that she would end her show this season after 25 years.

The guest lineup for "Surprise Oprah! A Farewell Spectacular" was a secret, but the show quickly delivered on promises from Winfrey's producers that the biggest names in Hollywood would be there.

Tuesday's taping will air May 23 and 24, before Winfrey's final show on May 25.

Madonna told the crowd that she is among the millions of people who are inspired by Oprah.

"She fights for things she believes in, even if it makes her unpopular," Madonna said.

Josh Groban and Patti LaBelle sang "Somewhere Over the Rainbow" as Winfrey, in a long purple dress, sat in a white chair onstage.

"Was that not the coolest?" Winfrey said when they finished.

The stadium was decorated with pictures of Winfrey at seminal moments over the course of the talk show. Boxes of tissues were on scattered seats throughout the audience.

Harpo Productions received more than 154,000 ticket requests for seats to Tuesday's event. Tickets were free and distributed to fans through a lottery. About 13,000 fans were at Tuesday's tapings.

Fans started lining up outside hours before the taping started.

Cathy Deters, 52, of Cincinnati drove to Chicago without a ticket, but someone outside the stadium gave her one.

"I don't think anyone could replace Oprah Winfrey," said Deters, an energy broker. "Not many people will have the chance to experience this."

Celebrities such as Lisa Ling, Carson Kressley, Jessica Seinfeld, Ally Wentworth, Bob Greene and former Chicago Mayor Richard Daley sat in the audience.

The content of the final episode of "The Oprah Winfrey Show" is still under wraps. Winfrey announced in November 2009 that she would end her popular talk show after 25 years.

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AP reporter Alicia Rancilio contributed to this report.