I Know What You Did Last Summer

For the novel by Lois Duncan, see I Know What You Did Last Summer (novel).
I Know What You Did Last Summer is a 1997 thriller/slasher film starring Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe, and Freddie Prinze, Jr. The screenplay was written by Kevin Williamson, writer of Scream, very loosely based on a popular novel by Lois Duncan of the same title.

The film was followed by the sequels, I Still Know What You Did Last Summer and the straight-to-DVD I'll Always Know What You Did Last Summer.

Production
Kevin Williamson's screenplay was purchased before his screenplay for the movie Scream. It was only after Scream's success that producers rushed Williamson's screenplay for I Know What You Did Last Summer into production.

I Know What You Did Last Summer Trailer

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The film was shot in Southport, North Carolina, which also served as the film's setting. Differences between the movie and the novel
Lois Duncan, the author of the book, was barred from the set of the movie. She was not aware of the drastic changes to her source material until she saw the completed film.
The novel is set in New Mexico, while the movie is set in North Carolina.
In the novel, the victim's name is David Gregg, not David Egan.

He is a young boy on a bike, and the novel's villain is David's older brother seeking retribution. He is not a fisherman, never uses a hook, and is not a killer, but he seeks to murder only Julie, due to Ray (after the hit-and-run accident) said that he would live in a world without her.
Instead of chopping off the Villain's hand or throwing him off of a boat, Ray hits him in the head with a flashlight (incapacitating but not killing him).
In the novel, Barry is driving the car, and it is a hit-and-run accident, not a cover up.
For the movie, Elsa and Helen's last names were changed from "Rivers" to "Shivers."
In the novel, Helen works as a weather girl for the local news station; she is successful enough that she can afford to live at The Four Seasons, a swanky apartment complex.

I Know What You Did Last Summer Part 2

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In the movie, Helen lives at home after failing to make it as an actress in New York, and she works for her father's department store.
In the novel, Julie is a year younger than Barry and Ray, and is at the end of her senior year in high school at the beginning of the story. In the movie, Julie graduates the same year as Barry and Ray, and is struggling with low grades at Duke University.
In the novel, Helen jumps from the bathroom window of her condominium to escape the killer.

In the movie Elsa is a pretty girl who is jealous of Helen's beauty.
There is no character Max in the novel.
In the novel there is no beauty pageant on the night of the accident, they go to a picnic spot in the mountains rather than a beach in the movie and they don't tell the story of the escaped killer.
In the movie both Barry and Helen (along with Max) are killed. Nobody dies in the novel.
In the novel Julie does not find a body in her car and Helen does not get her hair cut.
In the novel Ray and Julie go to the house to see David's sister but instead Helen goes with Julie in the movie.
In the novel David's sister's name is Megan not Missy.

In pop culture
The film inspired the Simpsons Halloween episode Treehouse of Horror X sequence called "I Know What You Diddily-Iddily-Did".

Spanish tv show Sé lo que hicisteis...

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(weekly "se lo que hicisteis la ultima semana" and monthly "se lo que hicisteis el ultimo mes" and specials "se lo que hicisteis el ultimo año") is a spoof of the spanish title of the film "se lo que hicisteis el ultimo verano"

The movie was mentioned in Aquamarine when Hailey, one of the charactors, said to Claire "he knows what you did last summer", about an employee at the beach hut of Claire's grandparents.

The movie is referenced in 'Horror Show,'a season 3 episode of Ghost Whisperer. Payne reads them out, and as he reaches 'I know what you did last summer,' he pauses, turns to Melinda, (played by Jennifer Love Hewitt) and raises an eyebrow before continuing.

Awards and nominations
Awards & Nominations for "I Know What You Did Last Summer" at IMDb
Reception
The film opened to $15.8 million in 2,524 theatres on October 17th, 1997.

The end result was a total of $72.5 million in the US and a worldwide theatrical gross in excess of $125 million.
Critics, however, were mixed in their reviews. Critic Roger Ebert wrote in his review, "The best shot in this film is the first one.