BtVS by Whedon and Mutant Enemy. Animaniacs & Pinky and the Brain by Spielberg and the WB.
Meeting a Challenge by CousinMary at Twisting the Hellmouth. I definitely recommend her Anita Blake and Batman stories.
Happens half-way through Season Six's 'Entropy'. The normal flow of events has been interrupted by the after-effects of a rather surreal dimensional breach in Cleveland. I'm still working on fleshing it out, but there's a decent summary later on in this chapter :)
A very cute box of baby wipes wandered into Sunnydale's Magic Box one day.
No... That's not right.
The cardboard box was upside-down and, from the two voices coming from underneath, probably wasn't moving under its own power.
Unless it did impressions.
"Watch it, Pinky! That's the second time you've nearly touched the artifact!"
"But Brain! I want to be the evil genius for a while. What does it do again?"
The deeper voice released a very put upon sigh. "As you just said, Pinky, it switches the powers of any two beings who touch it. We have come here because I want to steal the healing factor and speed of the one human who has the most acceptable rate of powers per lack of restrictions. The Slayer."
"But that's a female-only line... Zoinks, you aren't-"
"No, Brain. This will allow me to take her powers directly, working around even that little restriction."
Anya wandered by, going about her business in the shop she ran.
"Why do you want to do that, Brain?"
"To win the blasted contest and rule our world, Pinky."
"And why am I here?"
He sighed again. "Comic relief."
Anya wandered back and actually paid attention to the cute cardboard box.
"Please, oh please, oh please!"
"C'mon, now, Brain," shouted the wheedling member of the pair. "Just one little rub?"
Anya was terribly paranoid about certain kinds of rodents known for their breeding habits, so this bit of conversation triggered her terror response. As fast as she could, she jumped forward and grabbed the box before it could scamper away.
There was nothing underneath, so she flipped it over.
There were two little white mice on bicycles strapped to the inside of the box through a complex harness of rubber bands. She'd just turned them on their backs and they didn't look too happy about it.
"Oh, good." Anya sighed, relieved. "I was afraid you were... You wouldn't happen to be rabbits in disguise, would you?"
"I don't know," said the tall, lanky one. "Brain, are we?"
"No, Pinky," said Brain, with a shake of his oversized head. "If we were, I have hopes that even you would've noticed by now. And you, whomever you are, put us down now!"
"Oh, right." Anya rolled her eyes. "Like I'm about to let two rodents run around a magic shop without some very serious truth and anti-gnawing spells in place. It'd be different if you'd come in as customers, but no, you had to be sneaky about it."
"My dear," Brain began, in a polite drawl. "With all due respect... Bugger off! We're looking for the Slayer and you, whoever you are, are not her!"
"I don't think so," she said, turning the box at angle to get a better look at the shiny thing strapped to the back of the shorter mouse. "What do you have here?"
"No!" Brain yelled in vain. "Don't touch the-" He trailed off, Anya's fingers already having made contact with the object. If anything had just happened, it wasn't visible.
Anya, ignoring the mouse's words, freed the amulet from the little leather strap that secured it to his waist.
"Well, it's shiny," she stated, turning it over in her free hand. Her attention was firmly fixed on it at the moment Brain vanished. "I don't really know what it is... Wait, where'd the big-headed one go?"
"Albuquerque?" guessed Pinky. He'd seen his buddy disappear, but-
"Why would he go to New Mexico? It's awful dry and his hair would probably friz."
"Then his tail would match the rest of him! Poit!"
"You know... I like you," Anya said, moving the box and the strapped-in mouse closer to her face. "But, that's not going to stop me from prying every little bit of information about your plot against the Slayer from your rodent lips."
Once he'd managed to regain his focus, Brain spent several seconds experimenting with Anya's vengeance demon powers of transportation.
Unexpected, but... Useful.
He jumped back into the Magic Box just in time to hear her threatening Pinky.
"It's just as well," Pinky gulped. "I've sworn off larger women."
"What did you call me?" she yelled, shaking the box.
"Put him down!" Brain screamed. Furious, he teleported to Anya's right ankle and sank his teeth into her skin.
His strength had been enhanced by the stolen powers, so it packed quite a wallop.
Anya screamed and, kicking with her wounded foot, dropped both the box and the amulet.
As the box fell to the ground, Brain appeared in it.
The amount of teleportation power Anya had been assigned was a fixed amount based loosely on her human female mass. It was not scaled down to rodent size, so when Brain tried to take everything with him, the two rodents, their bikes and the box disappeared easily enough.
Anya ran off to tend to her wounds.
In her pain, she completely forgot about the amulet, which had fallen somewhere on the floor of her shop...
A bit of time passed before Halfrek, Anya's fellow vengeance demon, walked into the Magic Box to find her recently repowered colleague crying behind the cash register.
"Oh honey, is it Xander again?"
"No, worse," Anya sobbed. "I have all these ideas for Rube Goldberg devices filling up my head, but... I've forgotten how to handle money!"
"Hey, Dawn, the girls still at it?"
"Yep, Xander, it could take them awhile to crack the system. Oh, hey! You hear about Anya's phone call? Two white mice are trying to capture Buffy, so if you see her, you need to warn her."
"Really? They human-size?"
"Nah, regular, but they can teleport and bite real hard."
"Weird. So where's our favorite Slayer at?"
"Chasing down the usual suspect."
A Cemetery in Sunnydale
On discovering hidden cameras spying on herself and her friends, Buffy had decided to question Spike. That hadn't panned out so the conversation had led to other things.
"... you have to move on, okay? You have to get over-" Buffy said to the vampire she'd fought alongside, who had filled in for her when she'd died, who had loved her for a long time...
"Get out!" Spike snarled, halfway-justified. Maybe three-quarters...
Buffy stopped smiling her calm, collected smile (meant to show off her honest honesty).
Turning away, she walked up the short steps to the door of Spike's retro-fitted crypt, then opened it and walked through.
She ran straight into a certain young man named Oz.
The werewolf, ex-boyfriend of her best friend, looked particularly embarrassed about being in Sunnydale after his long absence.
And he'd brought 'friends'.
"I even feel like a completely normal, albeit outspoken, human again!" Anya complained.
"No, Anyanka," Halfrek stated reassuringly. "The magic that D'Hoffryn assigned to you is still assigned to you. I can feel the drain on the system like an extra ring on my finger."
"Well, I can't."
"Calm yourself. What we need is someone recently scorned with very low morals."
The bell rang as Spike walks in the door, leather jacket swinging. "Hey, I need a thing."
After he'd caught a glimpse of what Oz had brought with him, Spike had decided to sneak away, very, very quietly...
Anya immediately locked eyes with Halfrek.
"I didn't do it," the brunette stated, spreading her hands. "These things happen."
The recently blonde Anya shrugged, before yelling: "Spike! Hurry! I need to find out if I'm a vengeance demon or not! Wish something harmless and mean-spirited!"
"Hmm..." Spike spent a second in thought. "I wish Buffy would spend the next week bald. Then give her hair that changes color based on her mood."
"Granted," Anya yelled, waving her arms. "Oh, no! It's not! I'm not an awful veiny demon!"
"Well, that's good... Right?"
"No, it's horrible!"
"Will you make up your bloody mind!"
"Maybe it's because he's male," Anya guessed. "Hallie! Wish he was female so I can grant his wish!"
"Uh no..." Halfrek said. "You should be able to grant everyone's wishes, it's only taste that's held you back so far."
"I might add that, if you turned me female, I wouldn't be giving you a sodding wish. You'd be a demon, so I'd be able to drain you dry without this blasted chip in my head caring a whit."
"You know," Halfrek interrupted, somewhat fearful for her own demony neck. "I'll just go ahead and investigate this somewhere else."
The brunette nodded to the male vampire and carefully left the shop by the door, before teleporting away.
"Look, obviously you have things on your mind. I care, but I'm not in the mood. Rain check, alright?" Spike said.
As he stalked away, he accidentally kicked the amulet across the floor.
"Oh, what's this?" he asked, picking it up and turning it over. "Some sort of hairclip... No price tag..."
"Just keep it!" the distraught Anya gestured as she sat down behind the counter, returning to the complex physics problems she had suddenly found herself scribbling instead of dollar signs. "Some white mice, who could quite possibly have been midget rabbits, left it here and I don't have the slightest clue what it is!"
"Cartoons have come to Sunnydale, miss," Spike said as he rubbed the amulet with his patterned shirt. "If I were you, I'd stay inside."
With that, he left.
A little bit later and a bit too late, it occurred to Anya that the mouse... The other one had called him Brain... Just might have used the shiny thing to steal her powers and bookkeeping ability.
"Wait!" she yelled to the empty shop.
Just Outside Spike's Crypt
When the harrowing conversation was finally over, the one in brown and the one in blue leaped upon Buffy and planted kisses on both sides of her face, while the pink one launched herself at a particularly embarrassed Oz, throwing her arms about his head and her legs around his chest.
Staring directly into his eyes, she kissed him smack on the lips.
After landing on the ground at exactly the same time -a certain perfection only found among cartoons- the two brothers waved goodbye as their sister curtsied neatly.
Yakko, Wakko and Dot joined their gloved hands and begin spinning around in a circle.
The oddly named Animaniacs spun faster and faster until they were just a blur.
Soon, they weren't their black and white selves anymore... But three little orbs of red, blue and green.
The three points of light whirled in a tight loop, circling around the heads of Buffy and Oz, before zooming off into the night sky.
The word hung there, for a second, before evaporating into mist.
"I couldn't help but overhear what you were saying to Spike in that crypt," Oz began, turning to face Buffy. "I-"
"No, uh-uh, me first," the Slayer interrupted her werewolf buddy. "Let me get this straight. You're in Cleveland. You smell a rip in space-time. You investigate a deserted factory and find that someone left a dimensional portal on and, if left unchecked, it would shortly destroy the world."
"These things happen," he replied.
"You tried to shut it down, but were getting nowhere," Buffy continued, frowning. "When three monochrome creatures jumped out from the hole and offer to help save both worlds. You have an adventure. The four of you turn the machine off. They hop in the portal, just as it closes. But, it isn't over."
"They show up, about an hour later, saying that they have studied the designs and have figured out how to cross dimensions completely on their own. Then they say that you owe them and they won't leave you alone until they get my autograph. And you still don't know who created the portal in the first place."
"That pretty much sums it up."
"Okay, I can see why you want me to keep my mouth shut about your coming back to town for this very short visit." Buffy nodded. "You didn't come back by choice and feel that meeting up with Willow would not be healthful for either of you. She'd find your reason for being here to be both understandable and completely unbelievable."
Somewhere in Sunnydale
"In case you're wondering, I've still got my personality. I seem to have lost some of my knowledge of the inner workings of the universe... and gained some business sense... but my evil genius soul and dry wit are completely intact and with me still."
"That's good, Brain. Uh, I guess this is kind of fun for you, but could you please untie me now?"
After Brain freed Pinky from the straps they decided to teleport somewhere for an iced mocha.
"Are you pondering what I'm pondering?" the big-headed mouse asked the tall and lanky one.
"I think so, Brain, but even if vampires had chlorophyll in their skin they'd still need the same amount of blood. It's not like they'd be able to get enough sun for the little green things to do any good."
"No, Pinky," Brain sighed in resignation. "I was thinking that we should teleport inside the coffee shop's cash register, then buy our drink with their money."
"Why don't we just wait for someone to order what we want, then steal it?"
"Good idea, Pinky! I must finally be rubbing off on you."
"Uh, you now, or you before you traded up?"
"Shut up," Brain said, grabbing Pinky's long tail and teleporting them...
... This was a place of pure blackness... Definitely not part of the food service industry.
They were standing there, the only things of color in the place. Before them was a wall made of soft ebony foam.
"Zoinks," said Pinky, liking the effect.
Brain put his hands into the foam. "This is... This is... Something that wants to look inside of us... A Memory Soak!"
He turned to his gangly friend, saying: "Okay, Pinky. Reality is on the other side of this. It must be some stupid restriction on the use of this power. When we enter it, it should simply read our minds and let us through. I'll go first."
Before Pinky could reply, Brain flung himself forward.
The Memory Soak received a detailed description of the mouse's first encounter with a version of himself able to use magic. Of how this had only whetted his appetite for power and how he had built his portal and scoured dimensions for the means to obtain it... How they'd heard of the contest and why they had come to this reality...
Pinky saw the record of events form in the surface of the wall. When it finished playing, he held his nose, closed his eyes, and jumped in.
He left the black foam with an impression of some of the women he loved...
The horse he had lost his heart to and the sea lion that had never really understood him...