The creator of Squid Game, Hwang Dong-hyuk, developed the show in 2009. However, it was rejected by media companies and actors for 10 years.
The phone number used in the series was a real phone number. However, the only difference is that it has eight digits in the series, while real numbers in South Korea always have ten. When the callers dialed that number, their phones automatically added the prefix "010", which turned it into a real number. As a result, the owner of it was called more than 4,000 times a day. Netflix later announced that the number will be altered.
Chae Kyoung-sun, the set designer, felt this was her most challenging project as not only did she have to create something child-like and whimsical, but also creepy and menacing in addition to the safety concerns for the actors.
Director Hwang Dong-hyuk cast Lee Jung-jae as Gi-hun to "destroy his charismatic image portrayed in his previous roles."
The scenes featuring Sae-byeok and Ji-yeong were written to show the two most innocent characters out of the other players as they were the youngest and had used their extremely limited time to create a close bond. It is a juxtaposition to Gi-hun and Sang-woo, who were childhood friends but had become increasingly distanced through the games.