You didn't mention it, but the Annoying Dog has been confirmed by Toby Fox to represent him. So if the Annoying Dog stole Papyrus's special attack, that means that Toby Fox intentionally chose not to reveal what the attack was but wanted us to know that he did remove it.

Where all my left brains at?

Dark.. Darker Yet darker... Sans please turn on the lights

The annoying dog is a representation of Toby Fox, he continuously steals papyrus's special attack so the players can't know what it is

there was one little thing that didn't convince me about this theory: how could gaster and sans exist simultaneously? but then I thought about it gaster was fractured through TIME and space, so maybe those half fragments ended up in a past time before the experiment so gaster ended up meeting his own halves without realising, creating that way a weird loop where sans and papyrus wouldn't exist if gaster hadn't fallen into his creation which was made with the help of sans

MatPat: *tells a bad joke* Left Brain: *wHeEzEs*

Undertale: *exists* Matpat: I dont need sleep, I need answers

When I saw the jumbled version of "Undertale" Matpat put up, my brain saw it as *_Nutdealer_* *I feel my sins crawling on my back*

Sans knowing about the sun has always been a mystery to me. It’s possible that he just forgot the word for it, but none of the other monsters seem to have seen it before. Strange.

Cool thing: in the unused song "song that might play when you fight sans" Gaster's theme appears in your left ear when wearing headphones

Also: Temmie sees another timelines. The price of the Temy Armor becomes lower when you die, but your death doesn't happen because you LOAD.

One of the cool concepts that I've found myself believing is that Sans and Pap were less CREATED by Gaster's split, and more that they took on ASPECTS he lost in being shattered. That Papyrus wasn't precisely a SCIENTIST, but maybe more of an engineer, given his apparent ability to create puzzles and the bookcase with fluffy bunny and advanced puzzle making. Sans, on the other hand, seems very much a scientist by trade. I think they were the ones most compatible for whatever reason. And so in them, a piece of him was stored. An aspect. A fragment. But that is just speculation ^-^

he literally has the same energy as that overly curious friend who speculates about everything and this is why I still watch game theory/film theory/other stuff

OMG, a three parter is actually released, it exists!!! IS THE WORLD ENDING??!!!?!?!

There's one more thing that makes this theory solid - the amalgamates themselves. Studying determination was not the end goal of the experiments - having the ability to merge monsters was. Sans and Papyrus, if they really are WD Gaster, would be the only monsters known who would be able to gain from these experiments.

This is an amazing theory it shows how much work you put into the episodes and how much time and effort it takes to edit them for us to watch. Amazing Mattpat just amazing

One detail you missed: sans is making puns because he’s the left side of the brain, he is trying to make an attempt at feeling emotions like his ‘brother’

Conclusion: don't watch Gaster-related things before sleeping

3:16 Learning from school: ❌ Learning from Matpat: ✔

Honestly, if Sans truly is one half of the previous Royal Scientist, it would make even more sense as to why Toriel is the only other person he cares about besides Papyrus. I always thought it rather odd that he'd have such a strong bond with her just because she was laughing at his jokes through a door, strong enough to promise her he'd protect the player character despite us being human.

( Meanwhile in the void )Gaster: Interesting theory

One thing.... SANS' EYE. HIS GLOWING EYE ON GENOCIDE. It glows from the left side. We don't see Papyrus' "Special Attack" and never see his eye(s) glow. If this theory is correct, I believe that his special attack would make his RIGHT eye start to glow, as well as unveil a power we never truly see from him. This could be mindless deduction, but I think that I'm on to something.

In Sans and Papyrus’ house the joke book in the corner actually contains a quantum physics book - further confirming your theory

Man this TRILOGY HAS BEEN LONG but! I love this trilogy so far! Man this is a great channel.

14:07 Three smiling people with the words "don't forget" Deltarune: 3 heroes who will save the world

Toby: good luck on gaster! Game theory: hold my beer

I really like watching these theories, because even tho there are parts of the theory that don't really convince me, I can grab what does convince me and re-arange that into something that makes sense to me and something I like.

Its great how MatPat makes actual quality content, this is quite literally the death of most theory channels

3:22 [Bo Burnham "Left Brain, Right Brain" intensifies] Sans: I am the left brain. Papyrus: I LIKE OREOS AND P-

"So why doesn't [Papyrus] have Gaster Blasters?" Underswap: "Let me introduce myself."

After watching the 3 video I sat on my bed for a good 5 minutes at least just prosesing what I just heard. This was so awesome thank you.

I also think that Flowey had a little bit of Gaster's pieces, and maybe got a little bit by accident when he was revived by Alphys.

Sans: I am the left brain I am the left brain, I work really hard till my inevitable death brain. You got a job to do you better do it right, and the right way, is with the left brain. Papyrus: I like Oreos and pu-cats, yeah, in that order. And I cried for like, an hour after watching toy story three.

I can only accept this theory if Gaster makes bad science puns and hates himself for it.

These theories were so beyond mind, before I started looking up theories and I played through the game for the first time, I started breaking some stuff I noticed down and came up with this. I thought flowey (considering he knew about saving and loading) used to be a player. Which is why he knew how to save load and all of that was in his boss fight.

I love your videos whether they are crazy theories or games that I don't like because I see how much love you put into them and that's the most important thing

To explain one thing that Matpat missed: The creation/machine that Gaster fell into is not a Determination injection machine, but a DT *Extraction* machine. It removes determination. Now, when monsters are injected with determination, they fuse with more matter/dust/monsters, and start to melt. Naturally, extraction of Determination could split a monster soul/body/mind. Thus you'd get two* monsters and the original husk, split on personality and ability. sans having greater power, Papyrus being, as Undyne put it, "pretty freaking tough." Now, as for the Husk and journal entry, I'd imagine what was left of the original Gaster, effectively empty of determination, tried to quickly fix himself by injecting determination. He recovers temporarily (as did Alphys's test subjects), and made the final entry while talking to Papyrus and sans. Then he began to melt. Who knows what sans and Papyrus did afterwards - trying to "go back" or "fix Gaster"...but ultimately, Gaster became a melted memory. Now, Memory is a good choice of words, as there is one other monster tied to Gaster: Memoryhead. Memoryhead is an amalgamate, but the only one to not resemble any known monster. It has a faint resemblance to a Gaster Blaster fused with a brain. It's bullet attacks summon smiling white faces (Gasters?). It has no physical substance - it talks through your phone and gains health by absorbing your attack. Also, a phrase it says is "Lorem ipsum docet", while a filler phrase in code, translates to "Pain teaches." Now, how did Gaster split into more than 3? Well, there are two possibilities. Firstly, Gaster is split across time and space, leaving "memories" of himself. Alternatively, they could be the remains of a Gaster who is soulless. Either way, the three Memoryheads confirm the sans-papyrus-gaster group.

Another thing that I found, is that Papyrus' main color of clothing is orange, whilst Sans' main color of clothing is blue. Orange and blue are complete opposites on the color wheel. That's not mentioning the fact that they are complete opposites in other ways. Sans is short, Papyrus is tall; Sans' font is rounded and small, while Papyrus' is tall and sharp; even Sans' speech is more humanoid-ish and deep, while Papyrus has a higher, more metallic sound to his diologue speech patterns.

this makes so much- i hope you find out more bc this is the farthest i have ever been to getting to the mystery of Gaster please make a part 4 awsome video i hope you keep making awesome content

This is BRILLIANT! Great work as always!

Sans has knowledge and some control over time: he is aware of timelines, saves and resets, can allegedly stop time, teleport, and knows you can "time travel". On the flipside, Papyrus is aware of space. He knows about the river person and snowman when no one else acknowledges them, he can tell you anything about the world whenever you call him; he can manipulate physics (he can make your soul susceptible to gravity, and we also see him float/ walk on air after your pacifist fight). He just seems less powerful because he has no desire to harm. Papyrus is emotion and sans is logical. Makes sense. Maybe they're just foils of each other

Me: ugh another notification from that comment a week ago Notification: Game theory: Gaster's identity revealed! Me: VIOLENTLY SPITS OUT TEA

I'm literally convinced. Perhaps my bias leans me towards loving any mystery long after the story concludes but man it seems too true to deny. This is Canon now

i came back top this after 5 years, and i'm still hooked on undertale.

Asgore may also have some awareness of space and time manipulation. *You tell Asgore he has killed you [x] times. *Asgore sadly nods

Not to mention that both sans and papyrus are the only monsters (as mettaton's a robot ghost) who don't visibly or audibly show a monster soul. Papyrus doesn't have one when killed in game and sans turns to dust without the usual heart(soul?) breaking sound. But that's just a comment! A largely ignored and disregarded comment! Thanks for reading!

Bruh this game is so intense and complex i love it

Be crazy that he put that level of detail in all of it. Since that kind of thing would take alot of research and prep work.

Sans has his blue eye on the left

When Mettaton asks the human who Alphys’ crush is, their conversations will be very different on depending what you pick. If you choose “Don’t know.”, Mettaton replies by saying that she has a crush on the unknowable who is always watching/listening and theoretical person who also happens to be “not real”. Alphys then says to Mettaton that she’s done research about alternate universes and that maybe one day she could meet “them”. It could be a reference to Gaster, his followers, goner kid, or other fun values.

There are so many universes, meaning sans being ness, or being half of gaster, they’re both very possible

I remember, I think it was several years ago, I took a picture of a light at a movie theater because it looked like a Gaster Blaster. I remember at the time I was both creeped out and super excited at the same time. Those things are so creepy looking.

This video is meeting all of my standards

my mind was not blown... it was shattered across time and space NICE VIDEO MAT

I've never played or seen Undertale before. I've heard of the cool music track, but that's just it. Listening to your three part series on Gaster's Identity has really gotten me interested in this game

I like that when you showed a picture of Papyrus wrapped in vines when you said how is Papyrus wrapped up in this.

Sans: Can bend space and time Teleport Is the most difficult boss fight Is a time traveler Makes bad puns Is very intelligent Papyrus: Likes spaghetti

4,000 comments and 21 views? Gaster BROKE KZfaq!

"Scientific with the Skelebros" Now that's a podcast I'd listen to

This is legitimately fascinating

I don’t know if you realised this but as you can see the colour of sans’ jacket is blue and papyrus’ costume is mostly red. As some people know the two sides of the brain are represented with two colours red and blue. According to Bo Burnham’s song the right brain is represented with the colour red and the left brain is represented with the colour blue. And as Mat claims Sans is the left and Papyrus is the right brain. So this may show that Toby Fox created the characters this way so he left a hint in their design. Idk this is my theory

Can we take a moment to appreciate the fact that Sans and Papyrus look like their fonts? Sans is curved and Papyrus has sharper edges. Just neat attention to detail

You make the best theories of undertale

mattpat: *literally shatters everything you thought you knew about a video game* also mattpat: OH WHATEVER

"Sans and Papyrus are more than mere brothers" *FBI open up*

Game theory: has an actual theory that has like 30 essays to back it up Me: well Gaster kinda looks like a skeleton sooo....HOLY CRAP Gaster’s sans’s father :0

Funnily enough, the leading theory is that Gaster is the Skelebros' father.

Forget about a thriller movie- this has more suspense, thrill, and mind blowing than one!

FUN factor: Fate of the Universe Number

When you said,”cool dude facade” it sounded so very like Bill Cipher’s voice.

I just love the beginning it's just so cool

I need only four words to tear your theory apart Skeletons don’t have brains

2017: I hAtE mAtPaT 2020: He's the only creator I watch and I'm sorry

And also, you might have missed sans's LEFT eye glowing.

I have a headache, yet I still watched it. With some HEALING tea, I hated the headache and sore throat.

I’m honestly convinced that when KZfaq dies, Matthew should work as a private investigator cause he can put together ALL the little details

Up next on game theory: Sans is Purple Guy

7:17 Like... "Deltarune"?

If Papyrus is capable of seeing and knowing about other timelines, it makes it even sadder when you know that in every genocide run, he always believes you can change, even if he knows that’s very unlikely.

i LOVED the recap intro

TAKE IT FROM ME, WHEN SANS.. IS SERIOUS, HE CHANGES FONTS FROM COMIC SANS TO SANS SERIF!

7:17 Imagine if he wrote Deltarune

Love the recap btw

Every now and then I come back to these videos just because they give me an excuse to revisit Undertale.

If colours are worth anything, the red of papyrus and blue of sans makes the purple of the lab

Wait.... Maybe THIS is why Sans gets so angry when you kill Papyrus. It's not that you killed his brother, but now they can never put them back together to become W.D Gaster! Honestly bet someone else has wrote this comment.

8:00 this point bothered me a bit because from what I remember papyrus actually makes a lot of jokes, even more than sans. When I actually think about it I can only remember sans making at most 4 puns in Undertale. He actually shows more physical comedy, such as his shortcuts, the roof of his station being filled with snow, stacking hotdogs on top of your head etc. Meanwhile papyrus does do a lot of word play and over all does more jokes than even sans. He also only does a few visual gags, such as jumping of the window and jumping over you after his fight. Just a weird thing that bothered me.

This is a wild guess but, even after this theory i think that Sans still cloud be Ness. Heres how: In the previous theory Matpat said that Ness used the phase distorter, which destroyed his organic materials and left only the skelet, and whent into the underground. In this theory its aplified that sans and Papayrus are 2 sides of Gasters brain, which dosent connect to the theory that sans is Ness. Here is how the both theories cloud connect. When Ness went throught the phase distorter, as Matpat said, everything organic was destroyed. What i think he missed is that brain is an organic material too. If his brain was destroyed that means he cloud'nt do a lot of actions, such as moving and thinking. If we take that into considerstion all that was left of Ness was an empty skeleton with a soul. Now, what if Gaster clound'nt bare what he had done and has gone crazy. One thing that cloud prove this is entry 17. In there Gaster says that everything is going darker, and that darkness cloud be the guilt of klling and destroying so many monsters. Here is where it gets intresting. At the end of entry 17 Gaster says "what do you two think". The "two" he is talking to cloudnt be monsters, because i dont think any monster whould talk to him after what he had done, what if he went so crazy he started talking to something that wasnt a monster, something that whould listen to him, something like, two empty skeletons, with nothing but a soul. Gaster starts to think of a way out of this torture and comes to an idea when he stumbels across 2 skeletal bodys. He wanted to dissapear, but he didnt want to be forgoten. He uses the 2 bodys he found to put the 2 halfs of his brain in, and knowing they have a human soul he infuses them with determanation so they gain enought energy to live. Since Gasters left side of the brain was more developed, Sans who got it, remembers gaster more and its more serious. After Gaster infuses two bodys with determanation he doses the same to himself so after he pulls his brain out he has enought energy to put it inside of the bodys. This cloud explain why he is melting. After the process is finished, Gaster is gone, and only thing that is left are the 2 skeletal brothers. Another thing that i wanna mention, that proves thst sans is Ness even more is Sans's height. He isnt very tall, he is the height of a Frisk who is a kid. Whelp thats my theory, i know it has flaws, but its the best i came up with, but more importantly thank you for reading this, you are very determend ;) Another thing i wanna ad is that Papayrus cloud be somone who came with ness, because his suit has similarities to earthbound, but thats a theory i might add someday, again thanks for reading.

Sans: I am the left brain, I am the left brain. I worked really hard till my inevitable death brain. I've got a job to do, I better do it right and the right way is with the left brains might. Papyrus: I LIKE SPAGHETTI AND PUZZLES! YEAH! IN THAT ORDER! AND I CRIED FOR AT LEAST AN HOUR AFTER TALKING TO FRISK ON THE PHONE! I AM THE RIGHT BRAIN! I HAVE FEELINGS! IM A LITTLE ALL OVER THE PLACE BUT IM HOPEFUL, HAPPY, AND I PERSONALLY THINK THAT IM GREAT! *whispers* I'll join the royal guard! Sans: Here comes a human, here comes a human. Shake their hand and trick them with a whoopie cushion. All of my puns are skeleton related and they're great, so grab a treadmill and trick people through time and space. Papyrus: UNDYNE, LOOK! I THINK I MIGHT BE THE ONE! THERES SOMETHING ABOUT ME, I JUST CANT DESCRIBE IT! Sans: great Papyrus: YOU ARE THE EARTH I AM THE GLORIOUS SUN! I WANT SOME SPAGHETTI, I JUST WANT FRISK TO BE MY BEST FRIEND. BE IT! Sans: alright now, Papy, you're acting crazy. Papyrus: NO BROTHER, ITS CALLED BEING PAPYRUS. YOU SHOULD TRY IT, YOU MIGHT LIKE IT Sans: i work hard to not break my promise to Toriel, you are worried about the things that Frisk is scared about. I'm punny and laid back, while you talk loudly. I am the calm one, you are supreme. Papyrus: YOU THINK THAT CROSSWORDS ARE HARD WHEN THEYRE FINE, YOU THINK YOU KNOW EVERYTHING BUT YOU DONT KNOW ANYTHING AT ALL. HALF OF THE PUZZLES WERE SUPPOSED TO BE MINE, BUT YOU FORGOT EVERYTHING. I KNOW THAT YOURE LAZY, BUT IM SURE NOT.

papyrus when he slips up: “ah crap now matpats gonna dissect me and my game.”

Another thing I realized is at the end of the game on the sunset scene. Papyrus exits the screen on the right half, And sans exits of the left half of the screen.

my question, what if someone plays the game so many times, that eventually they just dissapear? that sans and papyrus are forgotten? also, apparently chara remembers the timelines, because if you do the genocide route twice, *she gets scared of you knowing that you’ve done it before*

*UNDERTALE* is spelled in **caps** while *deltarune* is spelled in **lowercase** Another sans and Papyrus reference...?

Then again, Gaster could also be the skelebros dad. Think about it, if Gaster was deleted from everyone's memories, his sons would never had had a family at all, so it would be as if the skelebros just, "asserted themselves".

So the brothers are pieces of Gaster’s brain, but what about the rest of him? We see one of his shards in that room where he just vanished, I wonder if there’s more of him out there that no one has seen yet

Yes. This theory matches up quite well with a certain AU called "Handplates", although sans and PAPYRUS are made from the pieces missing in Gaster's hands.

I just realised. In the basement it says "dont forget." And in the credits song of deltarune at the end of the song, the singer says "Dont forget, I'm with you in the dark." I think it is a hint twards Ghaster telling Sans and Papyrus that he is still with them.

The thing is, i think W.D Gaster is more left brained than right brained explaning why sans is stronger.

Another thing about how paps knows just as much as sans is in the genocide route, he says the following "this is when your supposed to-" as if he knows what you should do for the good route

I remember watching this before going to bed when i was younger. I didn’t want to go to sleep afterwards.