So I've had this theory for a hot second, and only recently decided to finally sit down and write it out. This goes on for quite a bit, and is a little bit on the heavier side, as it has my predictions for the last dark side, and a bunch of little patterns that are interesting to point out, that mostly lead to angst.

Okay, enjoy! 

TL;DR is right before the little bonus thing at the end that's just more angst stuff for Logan that kind of applies. 

So if you've been in the fandom for really any amount of time, you will know about The Rainbow Theory. Basically, all it is, is that the sides colors will make up the rainbow, and it seems to be nearly canon. We have all the colors except one. And that color is Orange. 

Using the knowledge that this side will (most likely) be orange, we have a clue about him. That he's watching, and that he's aware of the audience. 

From 24:34 to 24:44, in the upper left hand corner there is a score in orange text, the number is '07734'. Now, if you were to put that number into a calculator and turn it upside down, it would spell out, 'hello.'

Now this is mostly common knowledge at this point due to the fandom (me included) absolutely losing it over the hint of a new dark side. Especially since he shows up seemingly out of nowhere. I just needed to get those establishing bits out of the way before I continued on with the theory so it's a tiny bit easier to track my thinking (I tend to not explain my points correctly before moving onto the next one so I hope I did a better job of it this time through).

He is speaking to us. He's not saying hello to Patton or Roman or even Thomas! They don't even notice it! He is speaking to the viewer, which leads to the question of what exactly this side knows, and more importantly what this side is capable of. 

There is also speculation that this dark side is going to be somehow attached to or the opposite of Logan. The opposite of Logic, that implication alone should be at least a little unsettling. Now, I love Logan, I love him a lot. But he does seem to have kind of not the best relations with the others at times. However, I do not think we've reached him actually despising any side, not even Remus or Janus. I think that is going to change. 

The color schemes Thomas and the team have been using are really clever. They convey a lot about the character just by having the color associated with them. They have also been working with the idea of opposites. And those opposites seem to conflict quite often. 

What I mean is, violet on the color wheel is the opposite of yellow. Virgil and Janus' colors. Now, it is very, very plain to see that Virgil and Janus do not get along. Whatever history they have is still up in the air for specifics, but it's obvious that they have one. And at least Virgil hates Janus. 

Red and green are also opposites on the color wheel. Even though they have barely interacted, it's clear by Roman's language towards Remus that they don't have the best relationship. Roman breaks down at the mention that him and Remus are similar. Also the funhouse simile, (DWIT: 35:56) "It's a little like, looking into a funhouse mirror,  but instead of a giant head, or, like, long legs and a tiny torso... It shows you... Everything you don't want to be."   That's more than enough evidence to prove they aren't on the best terms.

Now, onto blue. Blue, more specifically, Logan's shade of blue, is opposite to orange. And judging by the pattern we see developing with the opposite colors. Logan will not like the orange side one bit. Hold onto that piece of information for a moment while I make a few more predictions based on some more patterns. 

Someone has already pointed this out, (if someone will be so kind as to remind me of who pointed this out that would be lovely <3), but back in Moving On Part 2, in the background, there is a picture hanging on the wall that will typically change  to fit whatever topic they're currently on, (ex: it changed to a picture of Thomas preforming in the show he won the golden apple for when it was brought up, or a zoomed in picture of the children's book he made.) At 1:30 the picture changes to show Thomas doing the 'speak no evil, hear no evil and see no evil' poses. (Covering his mouth, ears and eyes) 

The dark sides and Virgil seem to each have a connection to one of these. 

Virgil: See no evil. (Embarrassing Phases: 7:32. Virgil makes the room go completely black, blocking everyone's field of vision while he changed Logan's costume.)

Janus: Speak no evil. (Self-explanatory)

Remus: Hear no evil. (DWIT: 5:36-5:48. Remus muffles the other sides conversation, making Thomas hear him clearer than anyone else with the "Have you ever imagined killing your brother?" line.)  

The last one in that same vein, would be 'do no evil'. 

So what does this pattern have to do with the other patterns I've pointed out? 

Well, in order to get there, I need to point out, yet another pattern. (I'm so sorry)

Logan has always been a bit more physical than the rest of the sides I think. I don't really like using pre-Fitting In information in my theories, as I'm unsure of exactly how much they had planned at that point?, but I'm unsure of how to explain my point that well without this example. In Accepting Anxiety part 1, at 6:36 you can see Thomas rubbing the back of his head where he was hit with the laptop, immediately after, you can see Logan do the same thing. 

To me this sort of establishes that what happens to Thomas can happen to Logan, making him a bit more of a physical presence than the others. The brain is what stimulates pain after all, it controls all the nerve endings and pain receptors. 

Another much looser example, is his puppet choice in LNTAO, the whole 'not made of felt' thing was most likely just because of what Logan said that y'know, he didn't feel anything. It is also the fact of, all of the others puppets had felt somewhere on them, except his. Which makes the puppet, in contrast, feel more sturdy and physical. 

I don't think this one applies all too much, but it is worth noting that out of all of the sides, Logan tends to always end up holding something/having something more physical in his position more than the others. (Moving on being the exception)

The note cards.

The yerkes-dodson curve chart.

In Can Lying Be Good he was given a little headset.

Logic Vs. Passion he had a notebook (Which also made an appearance in Embarrassing Phases) as well as the drawings and graphs, while he wasn't physically holding them, they were real and not animation like Roman's examples.

(If you wanna count the crofters go ahead...?)

LNTAO also had the paper ball throwing physically hurting Roman.

In SvS when he was summoned (lmao summoned to appear in court I just got that as I was typing this out.) He is holding a law book.

In DWIT he gets physically hurt, twice. Having his teeth pulled out, and the throwing star. [Side note: the little interaction at 19:07 could also apply here, showing how he's more grounded as he stays almost completely still when Remus practically jump scares him.]

In the Healthy Distractions video he has what I'm assuming is coffee- 

Then in the redux, he physically ends up hurting Patton by popping up too close. An odd little detail that really didn't apply, don't you think? And it's immediately followed up with Patton reiterating that they were just figments of Thomas' imagination. 

Logan is much more grounded in reality and more physical than the other sides. Which is a very good thing for Logic to be, that's what it has to be. 

Now what is the actual theory?

Virgil can blind the others

Remus can mute the others 

Janus can silence the others 

My theory is that the 'orange side' is going to have the ability to physically or mentally control the others. 

And Logan is going to be his chosen victim, at least at first. 

Logan is going to have an antagonistic relationship with this side because of the fact that he takes control away from him. Which order and control is what Logan seems to thrive on! 

Keeping schedules, having everything in order, being taken seriously, attempting to make sure that Thomas is punctual, all of those things are Logan trying to maintain control. Now that isn't a bad thing in this circumstance at least, he's trying to make sure Thomas doesn't do anything that would cause his life to devolve into chaos. 

But when it's taken away from him it's going to send him into some kind of spiral, and lead to his two-part video. Losing control of things is scary as hell. It was one of the points brought up as to why Remus was being a pest more than usual (DWIT: 29:37-29:56). And obviously being ignored and pushed to the side isn't helping either. It could just be the straw that breaks the camels back.

Long story short, Logan's arc is going to be directly tied to that other dark side, at least in my predictions.

And it's going to hurt. 

Okay, this last little bit, is purely speculation, with very little connection to anything in canonicity. All of the dark traits seem to have a connection to some kind of animal, and they're typically ones that are seen as gross or creepy in some form, spider, snake, octopus. 

What if the last dark side's animal was some kind of bug? A beetle or something. Like seriously the thought of a bright orange beetle or cockroach is, disgusting. 

The only reason I'm saying this is because of a random thought I had. We all know Logan's 'robot' persona he puts up, he can't feel anything, he's mechanical, right? Well, a side coming in and completely flipping all of that on it's head, and ruining the control Logan had... 

That would be a real bug in the system, now wouldn't it? 

Well! Thank you for reading through all of this! I know it got a bit long-winded I just like having as much evidence as possible before stating a theory. 

But those were just my thoughts and I'd love to hear yours! So please tell me what you think!!! 

Thank you again! Byeeeee!  

TL;DR: My prediction is that the orange side will be able to take control over the other sides, and he will take control of Logan which would cause Logan to spiral enough to warrant his two part video. 

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BONUS: Some more angsty bits about Logan and control, that didn't apply to the theory too much! But could still serve as a bit of evidence! 

So first off, to me Logan seems like a very straight-forward (ha.) problem solver. If there is a problem there is no need to go through extensive loopholes or anything, no emotional mires or musical numbers unless necessary, the problem just needs to be fixed, period end of sentence. 

I have a feeling that Logan applies that same logic to himself. 

In the videos prior to Losing My Motivation, Logan was very very happy and bubbly. Easily excited and willing to participate in things he probably wouldn't have otherwise. He was much more expressive. (I know this is most likely because he was not a fully fleshed out character yet, but it can tie into some angst.)

Then in Losing My Motivation, Logan was brought the conclusion that he was the problem. (Note: this was also where the infinitesimal mistake was also made.)

From then on, we can slowly see minor changes to him in the videos, he starts becoming more reserved, serious, as well as trying new things to sort of fit in? (i.e the note cards) He saw the problem, and he tried to fix it. He became the definite voice of reason. Him smiling also went down a lot. 

Looking back on this better explains why Logan was so upset at the beginning of Logic Vs. Passion, 2:28-2:41. To him he's already fixed his problem, he's fixed himself, he was the problem, how could Thomas run into this problem again! 

Then we get to the crofters musical, where he just completely drops his walls down and sings and has fun with something he enjoys. Then of course, Virgil and Patton kinda come and unintentionally embarrass him. And he starts getting more feelings of inadequacy which build up to the whole problem of LNTAO. 

Then in SvS almost his entire time on the witness stand was Janus subtly poking at him, and at 15:04, he talks about wanting to make sure Thomas is punctual and productive. He in fact calls it his passion project, something he is PASSIONATE ABOUT. 

After two or three years, Logan is still trying to fix the problem. He's still trying to fix himself. 

Now this link to control is mostly in what Logan is trying to get Thomas to do, be punctual, follow schedules, produce adequate content at a steady pace, and follow the same pattern every day, according to the chart in Logic Vs. Passion. This habit forming, tends to nearly eliminate variables from Thomas' life. Earning Logan more control. Which is clearly what he's wanting, as he feels that is the way to prevent problems from happening.