1.The original title of the film was "The Décalcomanie."
2.The Kim family's house, alleyway, and neighborhood houses were all built on a set that doubled as a water tank.
3.The first floor and private front yard of the Park home were built in an empty lot in Jeonju, South Korea. A green screen was then placed on top and a second floor was added digitally. Each room in the home was built on separate sound stages.
4.The film was initially imagined as a play when Bong Joon-ho first came up with the idea in 2013.
5.Bong pulled inspiration from his own life. He worked as a tutor for a wealthy family when he was in college and often felt like he was "spying" on them.
6.Both Choi Woo-shik and Song Kang-ho had no idea what the movie would even be about before they accepted their roles in it. Both actors had previously worked with the director on other projects and trusted him completely.
7.Park So-dam also did not know what the film was about before agreeing to be in it. All Bong told her during their first meeting was that she would be playing Song's daughter and that she could refuse if she wanted to. She obviously didn't.
8.Bong was very anxious about whether or not Song would like the Parasite script. He even said that if Song didn't approve of it, he would have killed the project.
9.The word "ram-don" was created by the translator for the film and is a dish consisiting of two different types of instant noodles: black bean and spicy seafood flavor.
10.When the dad is looking at the forged documents, he actually says, "Seoul National University," but the captions read "Oxford." This is because Bong and the translator agreed that in order for the joke to land, foreign audiences had to understand the joke immediately.
11.Unlike most directors, Bong often demonstrated the performance for the actors, so all they had to do was follow his demonstrations.
12.Bong didn't realize he included so much water when writing the script, but did say it connects to the film's theme. He told an audience at TIFF, "rather than water being important in itself, water flows from top to bottom, and I think that's the tragic and sad element in this film."
13.Lee Jeong-eun — who plays the first housekeeper — also voiced Okja in Bong's 2017 film of the same name.
14.The song Kim Ki-jung and Kim Ki-woo sing before entering the Park home is actually a common song in Korea used to help school children memorize things.
15.The water pressure was tested in the scene where Kim Ki-jung smokes a cigarette on top of the overflowing toilet. They had to determine just how strong the sewer water had to be. Bong told GQ, "The special effects team prepared a lot to create that scene."
16.Choi Woo-shik recorded a song called "Soju One Glass" for the soundtrack, and it is co-written by the film's director and the film's composer, Jaeil Jung.
17.And finally, despite dreaming it up at the end of the film, it would actually take Kim Ki-woo 540 years to buy the home his dad is trapped in, based on his average salary.