So I recently watched the Pinky and the Brain series and was a little thrown-off by the multiple origin stories for Brain. I realize that it's a cartoon and all, but I like consistency! Luckily, I also like puzzles and creating my own head-canon XD
Which is what I've done here. Collected the information from a few episodes and turned them into a coherent (at least for me) story for The Brain that incorporates what was given to us as well as some extras I threw in to explain some of his behavior towards Pinky.
Un-beta'd so all mistakes are due to my idiocy! Also, Pinky and the Brain aren't mine or they never would've had to put up with Elmyra. And there would've been an episode in which they got married. Because... well. They had a kid and the episode was called Brinky. Plus they're shown more than once sleeping together. How much more evidence do you people need?
Anyway, my slashy views aside XD
He was a baby when he was taken. Just a week or two old, free to frolic about the field with the other field mice. He and his parents lived in a tin can that had an image on the side that he couldn't identify and truly didn't care overmuch about. He just knew that he loved the field, loved the other mice, loved his parents!
And that he hated the cage, hated the beings with tall legs and removable fur. The first time he'd seen one remove a long thing of white, he'd been horrified to see another layer of darker fur beneath. He didn't have such an odd fur pattern and neither did anyone else he knew. He hated the other mouse in his cage, too. He was taller, slimmer, and often had tears in his eyes. And he didn't smell of the field; he smelled... sterilized and liked to squeak about his parents and his sister. He didn't want to hear about anyone else's family! Not when he was so severely missing his own...
He decided to ignore the ineffectual animal and stalked to the far side of his cage, ignoring the long-legged beings as they made noises beyond his comprehension. But it was there that he first met the hamster, the one he soon figured out was called Snowball. It was the first word he learned to recognize as he and Snowball spent as much time together as they possibly could with the cage separating them. They made faces at one another and Snowball would laugh. They would run mazes, finding one another much sooner than they ever did the treats at the end. They would fall asleep curled at the far side of their cage, hands stretched out from between the bars, fingers touching.
He had never known such a friend, and it was such a comforting presence in the face of lost parents, lost childhood. And he was happy again, the can he'd been born in a faded memory.
He was hardly three months old when the happiness was wrenched from him again. It was a toy car, something in its steering going highly wrong. The little mouse didn't know what; he only knew the pain. Everything seemed shattered, broken, and he and Snowball would normally have been put to sleep then and there, but there was another man who said that he was working on a machine that could help.
And so mouse and hamster went through the untested and incomplete gene-splicer. For the mouse came healing, a wrench of pain that seemed small compared to all that he'd endured since the crash. When he lifted weary hands to his head, he'd discovered that it had gotten larger. He rose unsteadily, looking about warily. The explosion occurred then, sending him right back off his feet.
Snowball! The thought formed in his mind, made him dizzy. My friend! followed it and caused just as bad a throb as newly formed, entirely unused synapses began to awaken in his enlarged brain. He was thankful, though, when he caught sight of his dear friend. He ran to Snowball on unsteady legs, collapsing to his knees before him, fingers curling into his fur. He began a very gentle examination, searching for any injuries beyond the mildly singed fur and enlarged cranium, but Snowball waved him off.
"Oh, stop it," he muttered. "I'm perfectly al... right..." Snowball and the mouse blinked at one another several times before it dawned on Snowball what had occurred. "The machine! It worked!" He leapt to his feet, leaving the mouse staring up at him in awe. "Oh, it more than worked! Can you believe it? We can talk!"
The mouse opened his mouth, but only a confused squeak came out. He tried again, managed a grunt. The new machine hadn't worked entirely, had given him an ability to understand and process the words but not speak them. He understood the printed letters on the sides of nearby books, but it took him several, long moments to slowly sound out the words in his mind. Snowball rattled them off with such an enviable ease; the mouse could only smile warmly at him. Proudly. His friend, he reflected, had been given such incredible intelligence. Why... why they could do anything they wanted to do!
When, scowling, Snowball walked off, the mouse happily followed as he so often did. But Snowball didn't want to do the things they normally did, choosing instead to gaze at a globe that was on one of the countertops. He would stare irritably at the mouse when his attempts at conversation were met with nonsensical grunts and squeaks, attempts at a language Snowball didn't seem to understand any longer.
And that night, his dreams were full of the image that had once been on the side of a can in a field, an image he now recognized as the world. The globe! He was in the can, but didn't recognize it for the safety as it was. He had other ideas, other interpretations.
When he awoke the next morning, he knew what needed to be done. He waved his arms, jumping excitedly in place. For the first time in the mouse's memory, Snowball hadn't slept against his side of the cage. Even as the mouse recognized the oddities of this, the slowly growing synapses of his mind continued to struggle and couldn't quite explain why. He didn't understand that the unfinished machine had malfunctioned with him and with Snowball. With him, it had left the splicing incomplete. With Snowball, it had formed a darkness. Intelligence, in his case, had come at a price and he now considered the mouse beneath his notice. The little couldn't even speak!
But the mouse persisted and squeaked and called out in a wordless cry and Snowball that maybe, maybe the mouse would be able to speak if given the proper instruction. And then he would have a minion. His first minion. Snowball smiled. How delightful.
What was more delightful was the mouse's plan. Snowball realized quickly that, while unable to speak and unable to do math without some sort of calculator present, his old friend had been given an impressive mind. He drew quickly on a large sheet of blueprints, drew the world to scale with a giant bottle of super glue. With the calculations and scribbling before him, Snowball began to understand what the mouse couldn't articulate.
Global domination. How... marvelous. "Wonderful," he breathed and it was almost a growl. The mouse gave him a surprised look that was brushed away. "This is wonderful. Did you think of this on your own?"
It was answered with a squeak and several excited bobs of his head. Snowball decided to only be mildly annoyed at the lack of proper English.
By the end of the day he was more than mildly annoyed and, while the two were in their cages, he began lessons. The mouse would speak, if it were the last thing Snowball ever did.
"Neolithic!" he snapped. "Say it!"
"Nnnn... neeee... nnnn..." The mouse tried, struggled until his throat hurt. Finally Snowball gave a huff of breath and turned away to sleep on a bed of straw he'd formed the day before.
The mouse decided that it was an excellent idea and had done the same. He'd been shocked when his taller cagemate had pushed over more straw with hopeful, wide blue eyes. It was easy for him to forget that he even had a cagemate and this one was... well... hopeless. But the smaller mouse sighed and forged a bed for him nearby before dropping onto his own.
"Nnn," he tried again and again and again. "Nnnn-narf!" He rolled the word around his tongue, said it again. "Narf." He'd spoken. He'd spoken! He didn't know what it was, of course, but thought that Snowball might know. Snowball could speak already. Surely this was just a word he didn't know?
"Narf," he said again and rolled onto his stomach to sleep. He didn't see his cagemate watching him quietly, long tail beating against the floor like a happy dog's.
It turned out that "narf" wasn't a word. It wasn't anything. It was a failure, but it was all he could say when confronted with a word beginning with "n." "N-narf," he stuttered and Snowball rubbed a hand over his face.
"No! We'll try something else! Something simple. Point."
"Oh, enough!" Snowball walked away, somehow freeing himself from his cage. The other mouse didn't quite see how he had done it, so curled up in his straw bed and tried to say "point" while his cagemate ran wildly on the wheel. He was still watching.
"P-p-p-p-p-poit! Poit. Poit, poit, poit. Poit." He ran to the side of the cage, looked around wildly. "Poit!" he shouted, hoping Snowball would hear. "Narf! Narf! Poit!"
"What on earth is that disturbing racket?" Snowball came into view and the mouse smiled and curled his fingers around the bars of his cage.
"No, you imbecile! Point."
The mouse wanted to cry. "Poit?" But the hamster disappeared again, leaving his friend to sink down and wait. More words followed as he muttered to himself, joining the ranks of narf and poit in the nonsense that he could articulate. It never occurred to him, though, that his cagemate was listening. If Snowball was the first word the small mouse had learned, narf was the first the tall one did. With poit, zort, and troz following after. And he was absolutely amazed by the smaller mouse's ability to say these things while the one actually speaking internalized them as irritable nonsense. Narf, indeed his mind said.
Over the next several days, he tried hard to impress his friend with plots for world domination. Snowball would snatch the blueprints away at the end of each day and storm back to his own cage while the mouse would try and narf and poit his questions, seeking approval. His friend was gone. The mouse was having difficulty accepting or even processing the loss.
And then came the day that his incessant narfs grew to be too much for the hamster. With a howl of rage, he brought a pen down hard on the mouse's still-forming brain. It still hadn't quite grown to fit his enlarged skull and that blow halted its growth entirely. And, in some ways, reverted it.
The narfs and poits, zorts and trozs, grew entirely silent and the mouse could no longer even understand when his friend spoke. Enraged by this unforseen consequence, Snowball went on a rampage so noticeable that the usual blind scientists noticed and threw the hamster into the wild, no idea as to what they had just unleashed upon the world.
With his only friend gone, with a mind that had forgotten English and global domination, the mouse grew bitter. He began to bop his cagemate on the head in the hopes of inflicting as much pain on the tall mouse and had been inflicted upon him. He bit the fingers of humans, growled at other mice and animals, and was soon avoided by all. Even the cat - Precious - who mysteriously disappeared one day.
He was just over nine months old when a new duo was introduced to Acme Labs. Colleagues of the original doctor who had invented the gene splicer, these two were assigned Project B.R.A.I.N. They were charged with selecting two candidates to test this new version of the splicer, this time on two lab mice. Uninjured ones.
They chose the two cagemates. The smaller one for his enlarged cranium and vicious attitude, the taller one due to extreme stupidity. But the smaller one didn't want to do it. While the machine was a little different than it had been before, it was still not something he wanted to do. He'd been resistant to all of their experiments as of late, even though he could understand them even less than he'd been able to before. His memory of Snowball's disappearance was warped, seemed incredibly sudden. He could no longer even recall his brief periods of speech. Part of him wanted to insist that the dismissal of his friend had been in error, but he was just aware enough to remember that his friend hadn't been kind to him.
Lost in his thoughts, the mouse didn't quite notice when he and his taller cagemate went through the gene-splicer. And, while going through the splicer a second time should have ruined his mind and reverted him to his original state, the halted synapses were instead jump-started again.
They formed quickly, more rapidly than he'd been prepared for. He threw his head back and howled his pain. His cagemate put his feet in his mouth and giggled. This machine, this attempted gene-splicer was incomparable to the original. These scientists weren't the first, after all, only his friends. They had missed a step or two in the building process.
So while the smaller mouse's transformation was finally completed, the taller one only received certain gifts, baffling ones that he didn't have the mental stability to explain or even talk about. Realizing that he could make things float, though, had been cause for extreme delight until it had disappeared again. The one time the small mouse saw it, his only explanation had been, "Comes and goes."
But now, just after their transformation, the two were in their cage and the small mouse realized that he was... he was speaking! "I am... The Brain!" he exclaimed excitedly and could hardly believe it.
He had a wealth of intelligence now, but when Pinky - for the inane creature had decided to answer to the silly word when Brain had spoken it - proclaimed his narfs to the world, Brain felt the urge to bop him over the head. He couldn't have explained why, but the word drove him mad. The word that was not a word that had no explanation.
It only caused Pinky to laugh delightedly and soon, in him, The Brain discovered a new friend. And this one didn't leave when he failed. This one helped when asked, even when not. He knew when to wake Brain from a nightmare; he knew when to lift him into a big hug (though Pinky developed a tendency to do that for just about any reason); he just... knew.
So it was with Pinky that Brain attempted, night after night, to gain control over the world. The can was forgotten, his original plots were forgotten, his love of Snowball was forgotten. There was only Pinky and, when the mice ran into Snowball just a bit before Brain's second birthday, Brain was overcome with the possibility that Pinky might leave him as Snowball had done.
He nearly did, but when he came back Brain vowed to never let Pinky leave again. He needed his friend. He needed a friend. And Pinky, for all his faults, softened the hurt Brain had lived with for most of his life and offered him a permanence.
Night after night. Day after day. They were always Pinky and the Brain. And, though he'd never admit it aloud for fear of rejection, nothing mattered more to the small mouse than that.
So there. My head-canon for Brain. And Snowball and Pinky, I suppose XD
I can't quite remember all the episodes this information came from, but I do know Snowball and Project B.R.A.I.N. were the main two.