Standing nose-to-nose with her sister in the high-school library at the end of tonight's Halloween, Buffy Summers shrieked directly into Dawn's face, "You change back right NOW! Mom's gonna be home tomorrow, and there's no possible way she'll overlook this!"

Instead of replying, Dawn patted back into place her true-blonde hair that had become windblown from Buffy's bellow, let her bare arms fall at her sides, and then that young woman in the tight dress sent an evil smirk towards her sister's turning-purple features. Dawn would resume her normal body when she was darned good and ready. Plus, it was all worth it to get some measure of revenge over Buffy's nagging behavior earlier today.

It'd all began that morning. Joyce had unexpectedly announced to her children at the breakfast table that she needed to go out of town overnight due to a sudden business trip. So, instead of this mother escorting Dawn and her friends on trick-or-treating tonight, her youngest daughter would instead accompany Buffy when that older sibling fulfilled the Halloween task that a despised Principal Snyder had volunteered his students for yesterday at school. Neither Buffy nor Dawn had been the slightest bit happy about this, which meant when these sisters walked together to the new costume shop in town to chose their outfits, a battle royal had promptly erupted between the pair of Summers girls.

With Xander and Willow trailing along after, these only children had listened and watched in sheer awe, both ready to dive for cover at any second, as Buffy and Dawn noisily argued over what the younger girl would wear tonight. Dawn had at once eagerly seen the prospect of getting free tonight of parental supervision as her chance to dress up in something much more mature than she'd ever thought possible. Such as, a Dallas Cowboy cheerleader with the white short shorts, Britney Spears' "Baby One More Time" schoolgirl outfit, and anything else that'd finally get Xander's attention in the junior-high girl's secret campaign to cause that teenage boy to eventually make her Mrs. Dawn Harris.

Not that anyone else knew about the youngest Summers sister's intense crush upon that young man hanging back, yet still near enough to wince at Buffy's strident refusals to even consider such immodest attire for her sibling. The Slayer sternly told a sulking Dawn that just for bringing up those suggestions, her bratty little sister would wear tonight something totally safe, appropriate, and proper for her age. Something like Little Bo Peep, Wendy the Good Little Witch, or Sally Brown from the "Peanuts" comic strip.

As she confidently approached the costume store, Buffy was sure that she totally had the upper hand. After all, that young woman had the right of final approval over anything Dawn picked out, as decreed by Joyce when this mother had given her oldest child the money for their costumes. Feeling absolutely smug about this, Buffy ignored the sullen silence coming from the girl at her side, as the Slayer reached out to open the store door, already planning on finding the perfect costume to impress Angel tonight.

It really was a pity that Buffy didn't glance over at Dawn during this, as the older girl might have then seen the wickedly calculating look abruptly appear upon her sister's features. Dawn had just gleefully recollected something else that her mother had mentioned earlier today, before her children had left their house. In Joyce's exact words, she'd said, "…and get Dawn's costume first, honey, then yours…"

This meant that if Dawn felt like it, she could drag the whole thing out, look through every single costume in the place before picking one, and basically drive her big sister insane through the whole lengthy process. Best of all, under the ultimate threat of "I'm telling Mom!", Buffy couldn't urge Dawn to hurry up before the store closed and the older girl lost any chance of getting her Halloween costume. As she stepped into Ethan's Costumes, a malevolent smile that would have caused any sensible person to run for their very lives lifted Dawn's lips, as she inwardly cackled to herself over what was going to happen next.

Following after his favorite girls into the costume shop, Xander Harris had missed all this, with that boy only becoming aware of his absolute doom when a small hand possessing unexpected strength had clamped around his upper arm, with Dawn then joyously dragging along after herself this stunned male during her examination of each and every single outfit in the whole store. Now, ordinarily, Xander was properly appreciative of spandex and leather covering the female form, but not when someone he thought of as a little sister was asking his opinion of how well they'd fit on her. Nor when her much bigger and fiercer sister was breathing down his neck during all this and muttering dire threats into his ear if he even dared to think about saying anything that might be constituted as actual approval.

Fifteen minutes later, the back of his shirt soaked with terrified sweat, Xander frantically glanced around the room filled with racks of costumes. There wasn't any sign of Willow there, who'd earlier traitorously deserted him to scuttle off in search of her own Halloween attire. As if it mattered; she'd get the same thing she got every year, some kind of ghost costume. Meanwhile, a nice guy who didn't deserve any of this was about to have something horrible happen to him any second now. Either his brain was going to explode from shopping overload, or Buffy would use her Slayer strength to turn him into a zillion Xander-pieces the next time Dawn bumped her hip against his body.

Clearly, the only way he'd get out of this alive or without singing soprano was to find a costume for Dawn that both Summers sisters could agree on as appropriate for tonight's Halloween festivities. Now, what could possibly do that…? As he desperately eyed the various outfits around himself, Xander's notice was caught by a particular hue of one special dress hanging there. Making an instant decision, Xander thrust a pointing finger right at this garment, while hastily announcing to his female companions, "Hey, Dawnie, isn't that your favorite color?"

Pausing in the middle of their latest argument, both Buffy and Dawn gazed at where Xander was indicating. Their annoyed faces slowly changed into actual rapt consideration, as these sisters simultaneously recognized both the dress and the fictional character who wore it.

For Dawn, her first blissful thought was that Xander remembered her favorite color! Right after this, the girl identified the costume, and she admitted to herself that it was really nice. In fact, it was perfect! She actually liked that character, who was feisty and pretty, not to mention being aggressive in getting whatever she wanted. Of course, there was no way now she'd look exactly like the magical creature in her dress, since that person was a bit older, not to mention being much more developed in the chest and hip regions. Still, that green costume was sure to be tight enough while leaving her arms and legs bare, all enough to surely give Xander some hint of the future when puberty finally listened to Dawn's fervent invocations every night towards her bedroom mirror of "Grow, grow, grow."

As for Buffy, her suspicions over Xander's suggestion were lulled by the Slayer assuring herself that it was a freakin' Disney character! Totally appropriate for her younger sister, who was gonna wear it, or else! There'd been enough time wasted in all this, and she needed to check out further that really fine noblewoman's gown back there, even if Dawn had nastily said it made her butt look fat. Knowing she couldn't risk giving away her relief lest Dawn change her mind and kept on looking for the next couple of years, Buffy casually said, "I dunno, Xan. That might be a little too young for Dawn-"

"I'm getting it!" enthusiastically declared the named girl, letting go of Xander's arm and bustling over to remove the dress from the clothes rack. Holding up the hanger out in front of herself to check if the dress was the right size, Dawn beamed at seeing it would fit perfectly, and then she looked over at where Xander was shaking his numb arm to restore the circulation there, with her sister standing next to him and having a rather startled expression on her face. "Well, come on!" said the impatient younger Summers sister, who didn't wait for an answer from either of the other pair of teenagers. Instead, Dawn whirled around, the green dress pressing against her body, as the young girl strode towards the shop counter and its awaiting proprietor getting ready for his next sale, a rather malicious glint now deep in this Englishman's eyes.

Several hours later, Ethan Rayne finished the last word of his Chaos spell and what then occurred did so much faster than any human could possibly react to the consequences of this.

In physical terms, it could be likened to the following:

Plastic explosives plus Uranium-235 globe plus tritium equals hydrogen bomb.

Or, in magical terms:

Ordinary human plus Chaos magic plus magical dress equals the Key.

In its state of frozen time that the Key had set around itself a picosecond after being freed by that unexpected casting, this energy entity as old as the universe now had the opportunity to consider its surroundings. It was upon the surface of a minor planet of a not-very-impressive galaxy, inside the fleshy form of what was this world's dominant species. A rather immature body, too, which happened to live in close proximity to a dimensional portal. Effortlessly scanning every instant of Dawn's life back to the point when she'd been created by those Monks of Dagon and inserted into the Summers family without anyone (Dawn herself included) remembering this, the Key soon decided that while it'd been somewhat interesting being a human, enough was enough. There was no point in staying further in this form, not when the Key had regained its memories and would now leave, returning to its proper home in the cosmos. Still, this Dawn Summers had been an agreeable host, however unknowingly, so that young girl deserved a favor or two.

Without doing the slightest harm to Dawn, the Key separated itself from the body of this child, along the way doing a few little tweaks in reality which ensured that Summers sister would never know she'd once been the most powerful magical entity ever. Instead, Dawn's former life would now be absolutely factual, as if she'd been actually born to Hank and Joyce Summers, and having Buffy Summers as her older sister, eventually moving to Sunnydale with her family. Feeling a flicker of inward amusement, the Key decided to allow Dawn to retain the form and powers of the character she'd dressed up for Halloween.

Only for that specific girl, though. Considering that the Key had just used its powers to teleport the Janus statuette onto the surface of the sun, and also to deposit Ethan Rayne into the most secure magical jail on Earth, nobody else in Sunnydale even had time to feel the merest hint of dizziness during the infinitesimal period when the Chaos spell had been cast in that California city. The small group of people guarding the Hellmouth would never know just how one of their number had gained her newfound abilities, but since they were resignedly used to absolute weirdness in their lives, the Scooby Gang would undoubtedly come up with some kind of satisfactory story.

As for the town itself, the Key decided not to interfere with the Hellmouth. However, it wouldn't hurt to make things a bit safer for Dawn, so a thorough cleansing of this demon-infested city was promptly done by the sentient energy. Life of any kind was rare enough in the universe so that the Key didn't destroy any of those monsters it had exiled from their former home, but for two specific individuals now on their new planets, this wouldn't have been regarded as any kind of actual favor.

For Richard Wilkins III presently in his form as an Olvikan demon, this giant snake found himself the sole being on a grassy world where the only other life-forms there were various bugs and worms living in the ground. The Mayor soon realized with utter horror that he would be alone here for the rest of his life, and frankly, immortality wasn't all that it was cracked up to be.

In a distant world of endless night, Spike the vampire sucked out the last drop from one of the innumerable bloodplants around him in the unearthly forest that he'd appeared in. Dropping the deflated sac with two incisor marks in the wrinkled skin of the plant, Spike glowered around himself for a moment, until he felt a very odd sensation of strong nausea sweep over his body. That was only the beginning, as for the next couple of years, that vampire had to endure the horrific withdrawal symptoms due to coming off a century of nicotine addiction.

Just before leaving, the Key paused in its departure from Earth to carry out one last act. Then, as an emerald streak of light flashed upwards into the night sky over Sunnydale, a luminous-green entity was chuckling to itself over how furious Glory was going to feel after being transported back to her home. It was true that hellgoddess wouldn't suffer at all, even stuck inside the immense temperatures and pressures at the center of that planet, but by the few decades later that blonde skank had clawed her way back to the surface, her nails were going to be absolutely ruined.

Much later, after they'd finished escorting the trick-or-treating kids around town and returned to the Sunnydale High library, Buffy glared at where her little sister was floating in the air, delicate wings fluttering to keep her aloft, and her entire body covered with a sparkling yellow glow. Trying not to think that 'little" now perfectly described Dawn, what with her being just a couple of inches high, the Slayer snarled, "Will you get on with it! And remember, once you change back, don't ever let Mom know you can do that!"

Tinkerbell derisively stuck out her diminutive tongue at her sibling, to then swoop up and over in a graceful loop that took her several feet away from where Buffy was standing. Ignoring the gleeful whoops coming from below the library ceiling where Xander and Willow were gliding around in mid-air, a grumpy Dawn crossed her arms across her much-larger chest, to then dejectedly look down at her body in the short lime-green dress with a rigid trim, and green slippers with white puffs. She truly hated having to go back to her stick-thin adolescent form, now that in her fairy body, she really had curves.

Still… For some odd reason, a thought had just appeared in her mind, that a few years from now, a human Dawn would perfectly resemble below the chin who her character had been rumored to be based upon. At that time, Xander Harris was going to consider himself the luckiest man on the planet. Especially on their first honeymoon night, when that guy got to see an eighteen-year-old Dawn lying on their hotel bed, stark naked and crooking an inviting finger to her new husband, allowing him to start his closer acquaintance with the love of his life that looked just like Marilyn Monroe in her prime.

Author's Note: Besides Dawn being around for Halloween, there's another AU indication in this story. Drop me a line in the reviews if you spotted it!