The Story

While much of the story remains to be told, hints of a plot connecting multiple characters and settings have been found in a majority of MillenniaThinker's videos. The first official mention of a storyline being built by MillenniaThinker was in "Japanese Doomer", where MT stated in a pinned comment that he would be working on a "form of passion project" while continuing to upload regular videos. Whatever story has been told thus far is only enough to allow theories to be formed, but the rest of the story will be told soon (May 2021 MT held a poll on YouTube asking the fanbase if they wanted to see more of the established plot). For now, whatever facts we have will be presented below in a manner that allow for a general idea of what is coming to be formed.

Main Storyline, Major Characters, and Dynamics
The first mentions of a character being involved in some sort of conflict appear in "Doomer Eternal", where one of two demons mentions to the other, "You heard the Doomer is hunting us?". These monsters appear in later videos (more on that later). A few videos later, the first appearance of the Bogdanoff twins is marked in "Coomer World", where one of the twins speaks to a "Mr. Chairman" about a new world order, a "package", and a "Mr. Rothchild". Since then, the Bogdanoff twins have made regular mysterious appearances throughout the series, with "Mr. Chairman" being mentioned again in "Boomer Logic" and "Doomer goes Crypto". From here, the lines are drawn.

SUMMARIZED STORYLINE : The Bogdanoff twins, Technically Inept Boomer, the First Boomer, the Illuminati, Pepe, the Team, the Demons, the Second Team, Blonde Guy, and "He" are characters that are established as having major roles in the storyline. The Team is trying to defeat the TI Boomer, who is working for the Bogdanoff twins, who in turn work for Mr. Chairman (who is assumedly a member of the Illuminati) and are using the body of the First Boomer to try to implement a New World Order. The roles of Blonde Guy, Him, Pepe, the Demons, and the Second Team are unknown for now.

DETAILED STORYLINE :

The Team: The Team is first shown in "Day You Met KAREN For The First Time", where Chad Zoomer, Coomer, and Consoomer are sitting in the back of a van. Doomer, while speaking to Karen, says that his boss is "sitting in the back of the van", so it is implied that one of them is the leader, unless the "boss" is not shown. In "Doomer Stalker", Doomer is walking in the Zone and cries as he looks at a picture of his friends (the Team), this time showing Chad and a Boomer among the aforementioned members. In "Incel D&D", Nathan is shown to be on talking terms with Chad Zoomer, and later is seen with the Team in "VIRGIN with RAGE".

Several of these members have fought rounds against TI Boomer, who makes his debut in "BOOMER Vs TECHNOLOGY" fighting Doomer. Doomer opens Vault 69, unleashing Coomer in his Abomination form, who fights TI Boomer in "How to Beat The COOMER. It is assumed that TI Boomer is the same Boomer who fights against Consoomer and Chad Zoomer in earlier videos. It is worth noting that Big Brain Wojak appears with Chad Zoomer before he fights TI Boomer, but does not appear again until the debut of the Second Team, where he sits with them waiting for Simp, so a relationship between the two Teams could exist.

None of these members have been able to defeat TI Boomer. Coomer was close, but was distracted when TI Boomer employed pornographic material against him. This is where it is revealed that TI Boomer works for the Bogdanoff Twins, as he calls them after Coomer flees.

The Bogdanoff Twins and the First Boomer: The Twins have made appearances in many videos, but their goals have been hinted at from very early on. In "30 Year Old Boomer Fights For Jerusalem", the First Boomer defeats an army and takes posession of a horn (with a warning to not touch it next to it). In "BOOMER Vs Illuminati", the First Boomer crashes a meeting with the Illuminati and orders everyone out, saying he "came for [their] boss". Pinning down one of the Twins, he demands to know "where is He?". "He" comes out of a dark room and slays First Boomer. Several thousand years later, the Twins open the coffin of the First Boomer, which is reduced to a skeleton and holding onto the horn, and state that, "with this, we can wake up our Master again". The skeleton is shown hooked up to life support in "The Art of COPE". So, the twins are aiding Mr. Chairman to implement this new world order, while trying to bring "He" to Earth.

"He": The goals of "He" are unknown, as well as everything else about him, other than the fact that he lives on the Moon despite having been on Earth at one point (seen on the Moon in "Toxic GIRLFRIEND" and "VIRGIN with RAGE", and MillenniaThinker's Twitter and YouTube headers show the Moon with a red X-mark, with references to "He" written in red as well).

This is where the speculation begins. Aside from all mentioned thus far, only guesses can be made about the rest of the major characters. Theories on each follow.

The Illuminati: Existed around 5 thousand years ago. Shown to have a character of each type within their members, along with the Bogdanoff twins and Pepe, who are the only members known to live on to this day. Possibly working with "He".

Pepe: Shown to be a pharaoh in Ancient Egypt, and a member of the Illuminati. Implied to appear again in "Full Metal Boomer", where Drill Boomer refers to someone as "General" (whose skin is green and has a nemes on a shelf).

Blonde Guy: The most mysterious of all characters. Makes his debut in the 100K Special and appears four more times. Appears to Doomer in a dream (preventing him from killing himself) before vanishing from his room in real life. Appears to Nathan in a vision and prevents him from commiting violence against innocents in real life (in the vision, a Bogdanoff encourages a security guard to allow Nathan to continue walking into the crowd). Appears to be behind the motivational video that Chad Motivator makes. A God-like being, he has a pink haired woman (Coraline?) working with him, and is clearly one of the good guys.

The Demons: Have made multiple appearances in videos. One as a furry, one as a succubus, one stalking Brony (and Brony shown taking the form of a demon), one who attacks Toxic Daughter, one who attempts to dissuade Doomer. They clearly play a negative role in this, but who they are, who they work for or what their goals are remain unclear for now.

The Second Team: Members include Big Brain Wojak and Simp, along with a Boomer and 2 never before seen characters (the girl could possibly be Coraline, and the Kubrick-glaring male could be the same one seen in "Life of a Chad"). Their goals are also unclear, but they seem to be set up to play a positive role.

Other Connections/Loose Trails

 * In "Doomer go back" and "Happy Doomer Life", the number "23115216" appears ("2311152116" in Happy Doomer Life). In a similar fashion, seemingly random strings of 1's and 2's appear in "Female Twitch Streamer Logic", "Japanese Doomer", and "DOOMER CYCLE".
 * In "Full Metal Boomer", twice in "BLOOMER Vs DOOMER New Years Eve", and "PRO Gamers Logic", the same triangle is seen resting on the top shelf of different cabinets.
 * Daniel (Shy Guy) is shown to be friends with Nathan, but never appears as a member of the Team. Daniel introduces Nathan to the female reporter that Nathan later kidnaps, and Chad Zoomer is aware of this kidnapping, but remains nonchalant about it. The fate of the reporter is yet to be revealed.
 * Multiple times, characters have suffered from spontaneous wounds in the face/head that are elliptical in shape and can sometimes reveal teeth not unlike those of the Demons. Cuck and Brony are prime examples.