A deleted scene from Halloween H20 revealed an early intention to keep Jamie Lloyd canon after the series brought back Laurie Strode.
Until this seventh entry in the long-running slasher saga, Jamie Lee Curtis as Laurie had been absent from the franchise since its second installment. The third was narratively unconnected and by the time the fourth was in production, she’d established herself beyond the horror movies with which she began her career, and so declined to return.
In her place was created the character of Laurie’s daughter Jamie (played by a young Danielle Harris, who also went on to become something of a scream queen herself), while Laurie was written out by mention of her having died in a car crash. As Michael Myers’ niece, Jamie became relentlessly hunted by him, and is central to the events of Halloween 4: The Return of Michael Myers and Halloween 5: The Revenge of Michael Myers, before being brutally killed early in Halloween: The Curse of Michael Myers.
Halloween H20 brings back Laurie though by rewriting events to state she faked her death to escape Michael and now lives in California under an assumed name and works as the headmistress of a boarding school. We learned she had a teenage son, too, a little younger than Jamie would have been, while Jamie herself is not mentioned and inferred to have been removed from the continuity.
However, a treatment for Halloween 7 written by Kevin Williamson reveals the original intention was to keep the previous movies canon and address the presence of Jamie as part of them. A scene was planned to recount the events of the three preceding installments by way of an oral report by a pupil detailing Haddonfield’s bloody history. An accompanying excerpt from the script by Robert Zappia sees Laurie only learning of Jamie’s death in that moment, the overwhelming emotions and PTSD adversely affecting her to the extent that she only just makes it to a toilet before vomiting.
The script went through numerous revisions before filming on what became Halloween H20 commenced, straying far enough from the original vision that Williamson ultimately went uncredited, and somewhere along the line the decision was made to abandon continuity and simplify things by tacitly retconning previous events to have never taken place.