April 6, 2013 -- intro: Some of the most famous faces in Hollywood have passed through Port Charles, the fictional town where "General Hospital" is set.
These cameos have given actors a chance to play against type. Exhibit A: Sally Struthers, the daughter on "All in the Family" and later the earnest celebrity spokeswoman for the Christian Children's Fund's work with poverty-stricken children. In 2002, Struthers played Jennifer Smith, who kidnapped Luke and Laura in an attempt to get Luke to marry her (Jennifer, not Laura).
Click through the following cameos, and watch "General Hospital - The Real Soap Dish," a Special Edition of "20/20" hosted by Katie Couric, Saturday at 9 ET.
quicklist:title: Elizabeth Taylortext: The show's biggest cameo came in 1981, at the height of the Luke and Laura wedding phenomenon.
Elizabeth Taylor was a self-proclaimed superfan of the soap, and asked for the guest stint. Her five-episode appearance as the millionaire widow Helena Cassadine culminated with her putting a curse on Luke and Laura during their wedding.
Lisa LoCicero, a current cast member, recalled, "When she came on ... in the turban with the diamond and the whole thing, she was so cool, and she just kind of owned it."
In an interview for "General Hospital - The Real Soap Dish," a Special Edition of "20/20," Tony Geary, who played Luke, told Katie Couric that after Taylor's appearance on the soap, he and Taylor carried on a two-year affair.
quicklist:title: James Francotext: In intermittent appearances between 2009 and 2012, Oscar nominee James Franco played a serial killer named Franco with psychotic glee.
One of Franco's kidnap victims was Kelly Monaco.
"Playing with James Franco is like a kid in a candy store," Monaco said, laughing.
Mark Teschner, the show's casting director, said, "He came in, and we threw a lot of material at him, because we only had him for a limited amount of time. So he would shoot episode after episode, in one day. So we gave him quite a workout. And he did a great job of playing one of the most bizarre characters we've ever had on the show."
quicklist:title: Roseanne Barrtext: Barr, a fan of the series, appeared with then-husband Tom Arnold for three episodes in late March 1994. She played Jennifer Smith, daughter of notorious mobster Frank Smith. (This is the same role played by Sally Struthers in 2002.)
quicklist:title: Meredith Vieiratext: In 2002, Meredith Vieira, then the host of "The View," played the madam of an upscale prostitution ring.
"A lot of the stunt cast people, they come on, and it's like, which way to the hospital? And then the other actors are rolling their eyes on camera," said Soap Digest editor Carolyn Hinsey. "She could actually act. And she was a very convincing hooker, which I know she would take as a compliment."
quicklist:title: Katie Courictext: With all these cameos through the years, Couric couldn't resist doing one herself, she says in the "20/20" special airing April 6.
"I play a General Hospital nurse -- or do I?" Couric teases. "The only truth I can reveal is that I should stick to my day job."
Watch "General Hospital - The Real Soap Dish," a Special Edition of "20/20" hosted by Katie Couric, Saturday at 9 ET.