Kevin Williamson wrote this script before his screenplay for Scream (1996), but was unable to sell it. Following the big screen success of "Scream," Columbia Pictures immediately bought I Know What You Did Last Summer (1997) and produced it to capitalize on the newfound horror success. Because "I Know" is mostly a straight-up, modern update of the old slasher horror movie rather than a deconstruction of the genre, many critics and fans felt this was a huge step down from Williamson's more clever and innovative Scream scripts.
The rocky roads surrounding Dawson's Beach where Julie, Ray, Helen and Barry have their hit and run, and later Julie travels across frequently is the same mountainous road location used in the Alfred Hitchcock classic 'The Birds' (1963).
Despite being part of the main cast and appearing in many key scenes together, the characters Helen (Sarah Michelle Gellar) and Ray (Freddie Prinze Jr.) only speak to each other twice (Ray - "How do you know that?" Helen - "Missy said there was a friend named Billy Blue)" (at around 1h 2 mins) and (Ray - "No, it's not, it's true" Helen "Yeah, I don't think so, Ray") (at around 10 mins). Despite the fact that the two barely interact onscreen, Gellar and Prinze became good friends after meeting on this film. They later fell in love and married.
Writer Lois Duncan was vehemently opposed to her young adult novel being reworked into a slasher film, stating she was "appalled" in one interview. This was due to the fact that her youngest daughter was murdered by an unknown assailant in 1989. She said, "As the mother of a murdered child, I don't find violent death something to squeal and giggle about." Her original book wasn't that far off from a slasher though: it's still a bunch of guilty teenagers being stalked and terrorized by a murderous madman. It's just that nobody dies in her version, so in that sense it's more like an old school mystery.
One scene shows Julie at her breaking point, twirling around and asking the killer what it's waiting for, even though he's nowhere to be seen so it looks like she's talking to the air. When speaking with Us Weekly in 2018, Jennifer Love Hewitt revealed that that iconic scene was a kid's idea. "That scene was actually directed by a kid who won a contest to come on and create a moment for the movie, and it became the biggest part of the movie," she shared. She said that she had "no idea" where he was now, but that she wasn't thrilled about the idea of the scene at first. "He's like, " I want her to stand in the street and turn around and just scream. 'What are you waiting for, huh?'" Love Hewitt said. "I was literally like, 'Are you kidding me right now? This is what I'm gonna do? OK. This was a great idea.'"