SPOD

Note: Before proceeding, make sure avoiding spoilers if you're not a novel reader. This ship can be viewed as romantic or familial depending on the reader's region. SPOD is the slash/family ship between Secretive Plotter and Oldest Dream from the Omniscient Reader's Viewpoint fandom.

Canon
Both characters are gods, with Secretive Plotter being an outer god and Oldest Dream the most powerful entity of the whole story. Their pasts aren't very mentioned with detail in the novel, which is a similar trait both share.

During his journey, Secretive Plotter learns about Oldest Dream—the existence he believed was acting as his sponsor—was also the reason that the  and the scenarios existed in the first place. Upon getting this knowledgement that his sponsor was the main cause of his extended suffering caused him to become furious and he vowed to end their existence. In his last round (1863th Regression), however, upon making it to the Dokkaebi King and losing all of his comrades in the process, he learned from the King that he wouldn't be able to cross the Last Wall and reach the Oldest Dream.

There were times when Oldest Dream was mentioned indirectly by Secretive Plotter by referring to Yoo Joonghyuk from 1864th regression as their "puppet". Although, his identity wasn't revealed till later when KimCom were searching for the Oldest Dream with the intent of stopping his dreams (which meant they had to kill them). However, they fail due to Oldest Dream's rejection of their existence and the impregnatable barrier the boy erected around himself, making KimCom's back away due to his power. Right at that moment, Secretive Plotter emerges from Yoo Joonghyuk's body. The reason that he wasn't affected to Oldest Dream's barrier was due to OD's subconscious belief that nothing would stop the protagonist from the story (Secretive Plotter is actually Yoo Joonghyuk, who is also the protagonist from Ways of Survival). He stopped his mantra of "I am Yoo Joonghyuk" by declaring that he was the true Yoo Joonghyuk and then cut away Oldest Dream's Fables of suffering which kept Oldest Dream entrapped.

The 999th Gang, in turn, appear from Secretive Plotter's shadow, and saw Oldest Dream's Fables, which made them understand that the tragedies that occurred were just a boy's [Oldest Dream] coping mechanism of him imagining a world where he could be happy. They decided to put it to an end by embracing and giving him the companionship and love that drove him to the daydreams and left the subway together, Secretive Plotter included. Later on, the Gang made one last appearance to help 1864th Regression Yoo Joonghyuk escape from the Hounds while bickering about who gets to go to Kim Dokja's school on parent's day, which implies that Oldest Dream now lives the life of a normal and well-loved child.

Fanon
It's really controversial due to a possible age gap between both (Oldest Dream being possibly older than Secretive Plotter as he's mentioned to exist a bit more than SP), although the main reason of why it's hated by a half of the fandom it's due to OD's appearance both physically and mentally of a child. This is why fans prefer the ship as being a father-son alike, and along with the 999th Gang, they are all a family for Oldest Dream. There is a fan art where depict all of them, incluiding SP and OD, in OD's school on parent's day (the mentioned event being canon in the novel). For non-novel readers, the ship tends to be confused with Joongdok, as both characters' appearances are similar, but Dokja being smaller, although this is corrected by the novel fans although they use to prefer avoiding spoilers.

Although there are cases of both being shipped romantically, it's because of SPOD being a divine pairing version of Joongdok (most popular ship of the fandom), and as mentioned before, it's also due to SP being actually Yoo Joonghyuk after regressing 1863 times and Oldest Dream being a younger Kim Dokja who is the responsible for the creation of various world lines from the story, which made Ways of Survival become a fullfilled dream for OD. Though this is only in western media, especially in Twitter. Also, since Oldest Dream is mentally older in age, there are some fans who are okay shipping it. As SP had finally found his ◼◼, and OD finally got the ones who actually gave him love and care unlike his parents, both of them are drawn together along with the Outer Gods, though it's only in some cases as people tend to drawn the only two and the Gang are oftenly drawn apart. Instead of SPOD, fans tend to ship Plotja (Secretive Plotter and original Kim Dokja), as Kim Dokja is not only older, but the reason of why Plotter regressed for, but there are also others prefer the original Joongdok.

The massive hate on the ship it's due to fans blaming Twitter of depicting the ship as romantic, as in that media fan arts of minor-adults, familyships depicted as romantic, etc. tend to be common (example could be GoYuu and ChosoIta, from Jujutsu Kaisen), with this ship not being an exception. That's why for those who don't like the ship recommend deleting Twitter for not looking artworks related to the ship, specifically those who want to depict a possible romantic content of them. Although, the ship it's considered one of the most popular ships of the fandom, being the 10th most written on AO3 with there being 70 works available in romantic and 34 as gen. SPOD's name is also used sometimes in family/friendship terms and not necessarily romantic.

In fan fictions, SP's dream is having Oldest Dream, although being aware that he can't have his "god", due to to himself not being a good person. Although, this does not turn to be true, as OD also felt the same, and eventually get together.

Fandom
FAN FICTION

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TWITTER

Trivia

 * The ship name originates from their intials (SP & OD), forming "SPOD". Note that the characters' names are oftenly depicted by their intials on the fandom (example: Shin Yoosung = SYS).
 * If both of their names are searched individually, one of the first results will be the pairing between them (not SPOD, but Most Ancient Dream x Secretive Plotter/Secretive Plotter x Oldest Dream).