Wearing a glittering blue halter gown, the former first lady of California didn't appear to show any evidence of her recent marital troubles.
On Tuesday, the news broke that her husband, former California Gov. Arnold Schwarzenegger, has fathered a child outside their marriage 10 years ago.
"For more than 30 years you have bestowed upon me the most amazing friendship. You have shown love, support, wisdom, and most of all, the truth …," Shriver said, pausing for a moment after she uttered the phrase "the truth."
Winfrey responded by squeezing Shriver's hand tight, and the audience erupted in applause.
Shriver had apparently dined with Winfrey on Monday night, just before the news broke, according to People magazine.
An estimated 13,000 Oprah Winfrey fans and supporters gathered inside Chicago's United Center - just a few block away from Winfrey's Harpo Studios - for the taping of the two shows, dubbed "Surprise Oprah! A Farewell Spectacular."
The United Center is the city's largest sports and concert venue and the home of the Chicago Bulls and the Blackhawks. The NBA Eastern Conference finals between the Bulls and the Miami Heat had to be shifted to make room for the taping.
Just before 7:30 p.m. in Chicago, Winfrey took to the stage at the taping of her final shows to the tune of the Black Eyed Peas' hit song, "I Gotta Feeling." What followed was a star-studded extravaganza that electrified the audience.
Winfrey was met on stage by actor Tom Hanks, who told her, "You are surrounded by nothing but love. Thank you for what The Oprah Winfrey Show has meant for our lives.
"'Now Oprah, we all know that you do not like surprises," Hanks said, to which Winfrey replied, "I'm taking it all in."
Hanks continued, "Some might say that pulling off this party is darn near a mission impossible."
At that point "Mission: Impossible" star Tom Cruise walked out onto the stage.
The first hour of the taping also saw Halle Berry, Madonna, Diane Sawyer and other luminaries taking the stage to give tribute to Oprah. There was a big production number from R&B pop superstar Beyonce – she actually had to perform it twice because if technical problems the first time around -- and a performance by country music stars Rascal Flatts.
The second hour began with Will Smith and his wife, Jada Pinkett, as emcees. The first guest they introduced was Michael Jordan, who told Winfrey that she had "done wonders" for him.
"I know you have been a fan of basketball," he said, "but I have been a fan of yours for many, many years."
Next, Smith introduced Jamie Foxx, who sang Stevie Wonder's "Isn't She Lovely" -- with lyrics altered for Winfrey. When Wonder himself appeared on the stage behind a grand piano to take over the performance of the song, the crowd went wild.
Dr. Phil McGraw and Dr. Mehmet Oz also paid a quick tribute to Winfrey. The talk show queen helped launch their television careers. Simon Cowell also spoke, and he introduced a very svelte Rosie O'Donnell. She broke into a song and dance routine accompanied by men dressed in tuxedos.
Winfrey was clearly touched by the tributes, at times appearing joyful, surprised and grateful.
Eager fans started lining up outside the United Center early in order to see arriving celebrities and witness the end of an era.
Cathy Deters, 52, of Cincinnati, said she drove to Chicago without a ticket, but someone outside the stadium gave her one.
"I don't think anyone could replace Oprah Winfrey," Deters, an energy broker who was waiting with hundreds of other fans, told The Associated Press. "Not many people will have the chance to experience this."
In the days before the taping, Winfrey's producers were promising "the biggest names in movies, music and television."
"Celebrities from film, television and music feel a deep appreciation for the support they have received from Oprah and the show over the years," Sheri Salata, the show's executive producer, told the AP. "Oprah will be very touched by that gratitude."
The guest lineup was apparently a surprise to Winfrey.
"As most of our viewers know, being surprised is not one of Oprah's favorite things," Salata said. "In the spirit of our farewell season, she is making a rare exception, and we intend to make the most of that opportunity. It will be something to see!"
In the moments before the taping began, producers warmed up the already energetic audience.
One audience member, a man from Winnepeg, went up on the stage and proposed to his girlfriend. She said yes, and the crowd cheered wildly.
Staffers went on stage to instruct the audience in a variety of coded cues designed to surprise the talk show host.
In one such cue, they told the crowd that when they heard the phrase "Get your pencils out," they were all to wave the children's books they had been given before the show -- all to pay tribute to Winfrey's work to promote literacy. The books would be donated after the show.
Harpo Productions got more than 154,000 ticket requests for seats to Tuesday's event. Tickets were free; winners were determined by lottery.
The shows will air May 23 and 24. The content of the final episode of "The Oprah Winfrey Show," which will air May 25, remains a closely guarded secret.
Winfrey announced in November 2009 that she would end her popular daytime talk show after 25 years. And since then, she has pulled out all the stops.
On the final-season premiere of "The Oprah Winfrey Show," Winfrey surprised her audience with the news that she was sending them all on an all-expenses-paid eight-day trip to Australia.
The supersized surprise was presented with the help of John Travolta, who stepped out of a Qantas Airlines jet mockup to help make the announcement.
Winfrey has also brought back some of her favorite guests, including Diana Ross, Chris Rock, and President and First Lady Michelle Obama, as well as some of her most controversial -- writer James Frey and Inyanla Vanzant, the show's onetime relationship expert.
"Oprah is in great spirits, energized and taking in every last bit of these final days," Salata told the AP.
"The producers are a little teary-eyed -- it's hard to say goodbye," Salata said.
Legions of loyal fans are also in a state of disbelief that the woman who has been a daytime constant through four presidents, the Sept. 11 terror attacks, two wars and several recessions will no longer be there.
"She's one of us," Marianne Douglas of Rhode Island told "Good Morning America" anchor Lara Spencer. "She's our ultimate girlfriend."
Of course, Winfrey will continue her magazine and her new television network OWN, which launched in January. But it's unlikely that there will ever be anything like "The Oprah Winfrey Show" again.
Some fun facts:
The first national episode, "How to Marry the Man/Woman of Your Choice," aired September 8, 1986.
The average number of Americans who watch "The Oprah Winfrey Show" each week is estimated at 40 million, and the show is distributed to 150 countries outside the United States.
Total number of shows, including the finale: 4,561.
Total number of guests over 25 seasons: about 30,000.
The celebrity guests who appeared most often were Celine Dion (27) and Chris Rock (26).
Five U.S. presidents have appeared on the show: Jimmy Carter, George H. W. Bush, Bill Clinton, George W. Bush and Barack Obama.
The total number of items selected as "Oprah's Favorite Things": 283.
Winfrey and her show have won a total of 48 daytime Emmys.
In 25 years, about 1.3 million people have been in the studio audience for her show. For the final season, about 1.4 million people have requested tickets.
The audience for Tuesday's event at the United Center may not have been the largest for a taping of "The Oprah Winfrey Show." That distinction goes to the Season 24 "Kickoff Party" in 2009, when about 21,000 people closed down Chicago's Michigan Avenue to watch the Black Eyed Peas, Jennifer Hudson, Rascal Flatts and James Taylor.
A total of 65 books became Oprah's Book Club selections and nearly 2 million people joined Winfrey's book club.
More than $80 million has been donated to Oprah's Angel Network.
ABC News' Angela Ellis and Andy Fies contributed to this story.