This Is Your Life was an American documentary series broadcast on NBC radio 1948 to 1952, and on NBC television 1952 to 1961.  It was originally hosted by its producer Ralph Edwards. In the show, the host surprises a guest, and proceeds to take them through their life in front of an audience, including special guest appearances by colleagues, friends and family.  Edwards revived the show in 1971-72.

The idea for This Is Your Life arose while Edwards was working on Truth or Consequences.  He had been asked by the U.S. Army to “do something” for paraplegic soldiers at Birmingham General Hospital, a Van Nuys, Los Angeles, California Army rehabilitation hospital.  Edwards chose a “particularly despondent young soldier and hit on the idea of presenting his life on the air, in order to integrate the wreckage of the present with his happier past and the promise of a hopeful future.”  Edwards received such positive public feedback from the “capsule narrative” of the soldier he gave on Truth or Consequences that he developed This Is Your Life as a new radio show.  In the show, Edwards would surprise each guest by narrating a biography of the subject.  The show “alternated in presenting the life stories of entertainment personalities and ‘ordinary’ people who had contributed in some way to their communities.”  The host, consulting his “red book”, would narrate while presenting the subject with family members, friends, and others who had had an impact on his or her life.

By the 1950s, the show was aired live before a theater audience.  The guests were surprised by Ralph Edwards and confronted by the microphone and cameras.  They made their way to the studio during the first commercial break.  Most of the honorees quickly got over their initial shock and enjoyed meeting bygone friends again, as with Don DeFore on May 6th, 1953.  Movie producer Mack Sennett’s response was typical: he hated being caught off-guard, but as the tribute progressed he relaxed, and by the end of the show he was quite pleased with the experience.
Planning for the broadcast meant that some would know in advance about the surprise.  Carl Reiner later admitted that he knew beforehand about his appearance.  In some cases the episode was not a surprise: Eddie Cantor had a heart condition, so the show’s producers made sure that he was not surprised.  William Frawley receives a lifetime baseball pass from the Angels’ Fred Haney in January 1961.  Fred MacMurray also was part of the Frawley show.

Some celebrities were unpleasantly surprised.  Stan Laurel of Laurel and Hardy was angered by being “tricked” into what would be the team’s only American television appearance, on December 1st, 1954.  Laurel later said, “Oliver Hardy and I were always planning to do something on TV, but we never dreamed that we would make our television debut on an unrehearsed network program…I was damned if I was going to put on a free show for them.”  Lowell Thomas “displayed obvious anger and embarrassment”; when host Ralph Edwards tried to assure him that he would enjoy what was to come, Thomas replied, “I doubt that very much.”

According to The Complete Directory of Prime-Time Network TV Shows, one celebrity that was definitely off-limits was Edwards himself, who supposedly threatened to fire every member of his staff if they ever tried to turn the tables on him and publicly present Edwards’ own life.
Johnny Cash was caught off guard while filming a 1971 episode of The Johnny Cash Show.  He had finished welcoming the audience to the stage when his wife, June Carter Cash, walked onstage and introduced Ralph Edwards.  He tried to keep his composure, but was still seen nervous.