SEOUL - While the second season of Squid Game has new plot twists, one element of the Netflix mega-hit series where contestants down on their luck risk their lives to play children's games for the chance of winning cash prizes, has remained constant.

That is Young-hee, an innocent-looking robotic doll who in fact has a deadly role in the South Korean-made television series to find contestants to gun down playing the game "Red Light, Green Light" if she spots them moving.

Young-hee, who is clad in a simple orange dress and a hair clip, has become a viral meme on social media and the centerpiece of the streaming giant's promotional campaign.

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Chae Kyoung-sun, the production designer for Squid Game, said the doll's appearance had been partly inspired by her own daughter.

"My daughter had a bowl cut for a long time which was very cute so I decided to draw a very short bang," Chae told Reuters.

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"Her eyes are a little crazy. She's a killing machine and the movement of her eyes had to be easy to see, so we made her eyes quite big."

The initial inspiration for Young-hee came from a girl of the same name on the cover of old primary school textbooks in South Korea, though the killer doll was initially conceived as genderless, Chae said. The first season of Squid Game became the most-watched show on the streaming platform and expectations were high for the second season to replicate the success.

The new season of the dystopian thriller, released on Dec 26, also broke a record as the most-watched show in its premiere week on the streaming platform, with 68 million views, according to Netflix. The streaming giant said on Tuesday it gained a record 18.9 million subscribers in its fourth quarter thanks in part to the second season of Squid Game.

In 2023, Netflix announced a $2.5 billion investment in South Korea to produce Korean TV series, movies and unscripted shows.

Asked about the success of the show and this particular character, Chae put it down to their unorthodox nature.

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"How does this cute kid suddenly turn into a killing machine? - I think the creation of the Squid Game world by adopting unpredictable concepts and methods resonated with young people looking for fresh things," she said.

At the end of the second season, viewers also get a glimpse of Chul-su, a male doll set to appear in the next season alongside Young-hee that was originally envisaged for the first series.

"When they said there will be a second season and that Chul-su would appear, I brought back the drawings I had of Chul-su for the first season," Chae said.

"Think of it as a friend, a partner," she said.