Save the Green Planet!

Lee Byeong-gu, a conspiracy theorist obsessed with aliens, believes that extraterrestrials from "Andromeda PK 45" are preparing to invade Earth and that he must prevent their plot. With the help of Sunny, his childlike circus performer girlfriend, he kidnaps Kang Man-shik, a pharmaceutical executive who he believes to be an alien commander who can contact the Andromedan prince during a lunar eclipse that is due to occur soon.

Byeong-gu imprisons Kang in his basement and shaves his head to prevent him from sending a telepathic distress signal to the Andromedans. Kang is subjected to various tests which include scrubbing him with a Korean liquid painkiller and an “Italy towel” used by ttaemiris. It is revealed that Kang’s company poisoned Byeong-gu’s mother during a drug trial, linking Byeong-gu’s paranoia to personal tragedy. When a detective arrives to investigate Kang’s disappearance, Byeong-gu hides the evidence, but the officer later discovers human remains. He attempts to summon police backup, but is found and killed by Byeong-gu. Byeong-gu then crucifies Kang and breaks his leg after he attempts to escape.

Kang convinces him that a bottle of benzene in his car is an antidote for his comatose mother, and Byeong-gu takes it to her and makes her drink it, killing her. Meanwhile, Kang frees himself and uncovers his captor’s grisly research: bloodstained notebooks, jars of human organs, and photographs of victims. Reading through Byeong-gu’s diaries and journals, Kang learns of the man’s brutal upbringing: an abusive father, violent school years, his mother’s poisoning, family tensions, and his lover’s death during a protest.

The murdered detective’s partner locates the hideout before Byeong-gu returns. He captures both men, prompting Kang to claim that he is truly an alien. He says that the Andromedan race once tried to save humanity by altering human DNA. He promises to contact the alien prince at his industrial complex.

At the industrial complex, Kang activates a robotic arm that kills Sunny and overpowers Byeong-gu. The police arrive and shoot Byeong-gu, who dies wondering who will save the Earth in his stead, and Kang was abducted by an UFO after his arrest attempt.

The Andromedans appear and retrieve Kang, who is revealed as their king. Disillusioned by humanity, he declares Earth a failed experiment and obliterates it. An epilogue and credits show a video diary from Byeong-gu’s life, highlighting fleeting moments of happiness with his parents and Sunny.

• Shin Ha-kyun as Lee Byeong-gu
• Baek Yoon-sik as Kang Man-shik
• Hwang Jeong-min as Sunny
• Lee Jae-yong as Detective Choo
• Lee Ju-hyeon as Detective Kim
• Gi Ju-bong as Squad Leader Lee
• Ye Soo-jung as Byeong-gu's mother

Jang first conceived of the idea for Save the Green Planet! while watching Misery.^[3] He enjoyed it, but was disappointed with the lack of depth of the Annie Wilkes character, and accordingly decided that if he made a film about a kidnapping, it would be staged from the point of view of the kidnapper.^[3] Later, Jang stumbled across a crank website accusing actor Leonardo DiCaprio of being an alien who wanted to conquer Earth by seducing all of its women, and he decided to combine the two concepts.^[3]

In an interview with Kung Fu Cult Cinema, Jang said that the production cost around $3 million.^[4]

On the review aggregator website Rotten Tomatoes, 88% of 43 critics' reviews are positive. The website's consensus reads: "A funny and wildly inventive hybrid of various genres, Save the Green Planet! is definitely a unique viewing experience."^[5] Metacritic, which uses a weighted average, assigned the film a score of 70 out of 100, based on 14 critics, indicating "generally favorable" reviews.^[6]

In May 2020, it was announced that CJ Entertainment would be producing an English-language remake of the cult film with film-making duo Ari Aster and Lars Knudsen, whose credits include Midsommar and Hereditary.^[7][8] Jang was originally set to direct, but would later step down as director due to health problems, but remained attached as an executive producer.^[9] In February 2024, it was reported that Yorgos Lanthimos was set to direct the remake, with Aster producing alongside Ed Guiney and Andrew Lowe from Element Pictures.^[10] In May 2024, Focus Features acquired all rights outside South Korea to the project, which had since been retitled to Bugonia, starring Emma Stone and Jesse Plemons.^[11] In June that year, it was announced that the film would be aimed for a November 2025 release.^[12] In April 2025, the film was re-scheduled to be released in the United States on October 24, 2025.^[13] Jang stated that he was "delighted" and "relieved with Lanthimos's hiring.^[9]