Heather Michele O'Rourke was born in San Diego, California, she was discovered in the summer of 1980 by Steven Spielberg while having lunch at the MGM Studios Commissary with her mother and older sister Tammy O'Rourke, a dancer in the film Pennies From Heaven. Spielberg, who was preparing to film E.T., was also looking for a child to play the role of Carol-Anne Freeling in his upcoming production of Poltergeist. When he approached her, she said to him that her mother advised her not to talk to strangers.

Poltergeist was released in June 1982, and Heather's line, "They're he-eere!" entered American pop culture. Her success in Poltergeist immediately led to television work, and in 198283 she was a regular on the sitcom Happy Days, playing the daughter of Fonzie's girlfriend. In between Heather's numerous television appearances, Poltergeist II was filmed and released in 1986 and once again, she delivered another pop culture phrase, "They're ba-aaack!".

In early 1987, Heather became ill with what was eventually diagnosed as Crohn's Disease, and subsequently underwent medical treatment during parts of the filming of Poltergeist III, which took place in Chicago. Principal photography lasted between April and June of that year, with June 1988 as its scheduled release date, and by all accounts Heather finished her work on the film. After a family vacation, she returned home to California, apparently recovered from her illness. She remained healthy and symptom-free until the morning of February 1, 1988, when she became seriously ill and was rushed to the hospital where it was discovered that she had developed an acute intestinal blockage. Despite surviving emergency surgery, she died of complications caused primarily by septic shock resulting from the obstruction and ensuing infection.

MGM decided to re-shoot the ending of Poltergeist III in March 1988 using a body double stand-in. The director of the film, Gary Sherman, claims the ending was not a re-shoot, and that Heather died "before they could film the original ending." However, his claim is unsubstantiated, as the finished film was rated "PG" by the MPAA in November 1987, before Heather died. Heather O'Rourke was interred in the outer wall of the "Sanctuary Of Tenderness" mausoleum at Pierce Brothers Westwood Village Memorial Park Cemetery in Los Angeles, California. Her tomb is near that of Dominique Dunne, who played her sister in Poltergeist.

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