Just a mere second after hearing those chilling words "Wish granted!" echo through the hospital room, Xander Harris staggered under the sensory overload bombarding his mind. In between how his new body seemed to be in perfect health (unlike his previous enfeebled carcass) and how all of his senses were working at their highest levels, this former Sunnydale resident barely paid attention to the vicious struggle taking place a few yards away at the far edge of a Gotham warehouse's roof.

The ensuing eruption of mocking laughter coming from the Joker as this homicidal maniac leered down at a stunned foe now sprawled out in perfect helplessness on the roof's asphalt shingles swiftly brought Xander back from his justified daze. An appalled Xander then saw how the Joker happily tucked away inside a purple jacket his joy-buzzer gag ring which a moment ago had nearly electrocuted Batman. From this same inner suit pocket, an oversized Warner Brothers cartoon-style pistol was produced, and aimed directly at Batman's cowled head by a gleeful villain about to kill this pestiferous hero for once and all.

Acting solely by instinct, Xander surged up onto his feet from where he'd also been lying on the roof and raced forward. However, a few steps later, his feet got tangled together and Xander lost control of his body, tripping to begin a disorderly tumble which resulted in him slamming hard against the Joker's lower legs.

Taken by complete surprise, the Joker stumbled backwards…and then stepped off the fourth-floor roof.

With a disbelieving shriek very different from his usual sadistic hilarity, a flailing Joker plunged downwards and out of sight from the remaining pair left behind on the roof. Shakily getting up, Batman rushed over to where he could stare down at something he thought would never be possible.

On the warehouse's rear loading dock, the ruined body of the Joker showed this evildoer to be wholly extinct of life. Unlike all too many other times, there was no way for him to survive what'd just happened to someone who'd repeatedly terrorized the entire city of Gotham. Not when a despairing grimace was the sole remainder of a green-haired head which resembled a shattered watermelon, down to the red stuff inside sprayed everywhere.

A numb Batman glanced over at where Ace had just joined the man at the roof edge. This vigilante blinked, and then firmly shook his head to drive away the bizarre thought which had just popped inside his brain, at seeing how the dog somehow sensed Bruce's gaze to look up and produce what seemed to be nothing else but an…apologetic grin.

Taking a steadying breath, Batman cast one more look at where the Joker rested (hopefully already on his way to the deepest level of hell), before turning away and striding towards the trapdoor leading to the building stairs. Absently muttering "Heel, Ace," Batman otherwise ignored how the German shepherd obediently followed along after. This was going to be somewhat hard to explain to Commissioner Gordon. Just how was he going to tell Jim that his dog had accidentally killed the Joker?

Xander was busy with his own problems. See, the whole purpose of the w-word in the first place had been for him to join in the Dark Knight's adventures as first created by Bob Kane and Bill Finger so many years ago. Given that he was gonna kick the bucket any second now, why not go out with fulfilling a childhood dream? All right, all right, so he'd been pretty much hopped up on the really good morphine at the time, but Xander was positive he hadn't come right out and asked to be a dog!

Robin, sure, any of them, even Jason. If it'd indeed gone that way, Xander was sure he would figure out a way to take care of the Joker for once and all-

Another canine grin appeared on Xander's shaggy muzzle, this time much more evil than his earlier nervous smile. Well, he had, hadn't he? Gloat later, though.

Back to being one of Batman's partners: again, he'd meant one of the Robins, except now that he could clearly think about it, Xander wouldn't have minded all that much showing up as any of the others. That included even such characters as Batgirl (either Barbara or Cassandra), Huntress or Stephanie Brown as Spoiler. Why not? All his life since high school, he'd been around strong women. This time, see what it'd be like as the opposite gender. But not as Ace the Bat-Hound!

Xander's irascible mood at some unknown vengeance demon undoubtedly laughing their ass off at pulling such a great joke on him was interrupted by the pair of crimefighters coming out of the warehouse into a side alley. There, a sleek, midnight-black car with a bubble top and the front radiator having a large bat image awaited them. Opening the Batmobile's door for Ace, Batman told the dog, "In. Stay."

Without any hesitation, Xander again obeyed, jumping onto the passenger seat and curling up. Placing his muzzle on his front paws, this animal watched Batman go off after closing the car's door, surely on his way to make one last check on the Joker and then call the cops about that bastard's death. Fine with him, Xander thought. He needed some alone time.

Okay, it looked like Xander was stuck as a dog. Contemplating it further, this man in animal form tried to remember all he could about Ace the You-Know-What. Lessee, that character showed up sometime in the DC comics around the end of the 'fifties and made a few appearances for the next several years in various Batman issues. That time period matched this old-fashioned car, since Bruce didn't get a new one resembling the TV show vehicle created by George Barris until sometime in the mid-sixties.

Xander was rather relieved to recollect that it'd never been mentioned exactly how Ace stopped being Batman's pet. The writers back then just probably couldn't think up any more stories with that dog, but they never got around to killing Ace off, much less having a nice family adopt this German shepherd.

Sooo… what was he going to do about it? Experimentally, Xander tried to say his name out loud. In the Batmobile, a rough voice managed, "Zzzaannndrrrrrr."

Good, that settled it. If absolutely necessary, he could tell Bruce everything (and wouldn't that be a hoot). Was Zatanna around? Nah, not right now, but there were other people here more than familiar with magic, Dr. Fate for one. That gave him a honest chance to turn back into a human whenever Xander wanted.

Idly scratching at an ear with a rear paw, Xander considered this. What the heck, no need to rush things. See how the next couple of days went, all while hanging around with Bats. He'd really love to check out the Batcave, meet with Dick and Alfred, that kind of thing. In the meantime, be the Batman's loyal dog, ready to go out every night with his master to protect and defend Gotham from the scum of Arkham Asylum.

In the Batmobile's front seat, Xander grinned again. Now that he knew he wasn't permanently trapped as a large pooch, this Scooby was seeing the funny side of it. Sure, go ahead and do the whole 'masked superhero animal sidekick' bit. Who could resist meeting with Krypto and Streaky and Comet and Beppo, better known as the Legion of Super-Pets? Plus, it'd be hilarious if Xander could get away with as much trouble as possible before Bats figured it out. If he ever did.

An unnervingly dangerous glint appeared in the dog's eyes where he was seated in the car, indicating an abrupt change of mood. The Joker might've been the worse of the lot, but Xander had no sympathy nor mercy for others of this villain's ilk. If he was in Gotham for real, might as well as do some additional clean-up, just to make things a bit more exciting. It all depended on how Xander felt at the moment, whom exactly he was dealing with, and how to best accomplish it right under the nose of a certain dark avenger of the night.

Oh, yeah. Maybe if that vengeance demon ever showed up in the coming days to see the consequences of their prank, a battle-hardened Xander wouldn't hurt them too much…

All it took was a single "Fetch, boy!" by an enthusiastic Robin for the Penguin to be repeatedly found by Ace the Bat-Hound no matter where Oswald Cobblepot hid in Gotham and then dragged by the collar of his tuxedo to the nearest police station. Yes, it was true this master criminal completely fed up with so many undignified occasions caused by that blasted canine had based his felonious exploits on bird-related misdeeds, but that didn't mean he deserved to be actually retrieved like a wounded duck during hunting season!

A quite disgusted Cobblepot, having no other recourse, ended his lawbreaking activities and decided to open what would soon be a very popular nightclub. Where no dogs whatever were allowed.

When it was finished, Scarecrow having been rushed to the hospital with all-over third degree burns due to his costume bursting into flames which undoubtedly crippled him for life, the World's Greatest Detective had no trouble locating the half-empty box of kitchen matches covered with doggy drool. What confounded Bruce the most was just how did that German shepherd learn to light these while gripping one match in his teeth?

In the middle of Batman already out cold from chloroform and stuck in one of his death traps, Harvey Dent, also known as Two-Face because of an acid attack years ago which completely destroyed the left side of this lawyer's face while leaving untouched the other side, held in one hand his lucky coin. That same coin would determine in the next few seconds the fate of his enemy. As per Two-Face's regular custom, he'd flip the coin up in the air and when it came down as either as a scarred head or an intact tails, that would decide whether Harvey would immediately kill Batman or just walk away and leave him there to escape sooner or later.

With a flick of his thumb, Two-Face sent the coin spinning high in the dimly-lit construction zone. Not more than an instant later, there was the soft scrabble of paws, and from out of the darkness, Ace the Bat-Hound leapt at his master's enemy. A rare flash of mutual fear contorted both sides of Harvey's face, and he flinched away at the angry dog with this dangerous beast's jaws wide open and showing every sharp tooth in the course of his jump…which wasn't headed directly at Two-Face.

Instead, as he sailed through the air, Ace twisted his neck and expertly snapped at the descending coin, catching it in his mouth like it was a yummy snack tossed at him. At the same time the dog landed back on the ground with all four feet, a deep gulp was heard issuing from that exact spot.

Harvey stared in disbelief at where the dog had just sat down on his haunches and stared right at the human. Next, Ace slowly licked his chops with real satisfaction and then sent what was nothing else but an actual smirk at Two-Face.

Starting to realize just where his lucky coin was and how it'd eventually reappear, the very last of Harvey Dent's sanity crumpled away, leaving him in a permanent state of catatonia. A thin trickle of drool dripped from the corners of this man's slack mouth as he gazed blankly ahead.

Getting back up onto all of his paws, Ace trotted over to where a now-stirring Batman was tied to a steel I-beam laid on the ground. Commencing to gnaw at the ropes wrapped around the Caped Crusader's wrists and ankles, Xander cautioned himself not to snigger out loud at what Bruce was going to find when he finally woke up. Tonight's whole brand of weirdness was definitely gonna drive Bats…batty.

Thinking it to be only a minor bit of aggravation in the course of their usual duties, the caretakers of one of Gotham's parks repaired a deep, water-filled hole apparently dug in the ground by a stray dog at one of the public recreation area's more remote locations. The only mysterious thing about it was how someone passing by inexplicably dragged over the hosepipe from a nearby utility shed and turned this on and off to fill up the pit to its brim with now-muddy liquid.

Xander himself thought afterwards the hardest part of luring Clayface to the pit and shoving with a brisk nudge of a furry shoulder the entity composed of earth instead of flesh in there was operating without a opposable thumb the faucet which rapidly sent enough water to completely dissolve that monster into lifeless goop.

After finding Mr. Freeze's decaying corpse in a hidden lab under one of the city's ice-making facilities when the day-shift workers complained about the smell coming from under the basement, the Gotham police force discovered this man requiring unvarying subzero temperatures to survive had his protective cyrogenic suit short out for some reason. Further investigation turned up an electrical cable with chewed insulation leading from the suit to an emergency generator. Also on the cable was the faintest trace of animal urine.

Edward Nigma abruptly woke up one night in his appropriately decorated lair with numerous question-marks everywhere. Including the bedsheets. It was not one of his more enjoyable moments, because nobody wants to find they're sharing this sleeping furniture with something under the covers which just chomped its jaws almost shut onto the crotch of his green-and-black pajamas. It didn't hurt, but this might change any second. Without moving any other part of his body, the Riddler cautiously turned on his bedside lamp, to see there leaning against the bottom of this appliance a nearly illegible note scrawled in pencil. Squinting at the note, Edward read:

Here's a riddle for you: Which is better, retirement or castration?

Peeking under the covers, Edward looked at Ace the Bat-Hound lying between a pair of wide-apart legs and still performing there this dog's menacing clamp all while beginning to slowly increase the pressure. He promptly answered, "Retirement! Now, let go!"

A man obsessed with puzzles and riddles soon afterwards invented the numbers game known as Sudoku decades earlier than it happened in our dimension. Mr. Nigma became a lot richer than he ever dreamed of as one of Batman's regular opponents. And it didn't involve being habitually punched by a vigilante into unconsciousness, or worse of all, encountering that damn dog ever again.

In all these sudden deaths, mishaps, and disappearances, the Gotham Post had only a two-line obituary appear concerning Dr. Hugo Strange perishing in an automobile accident, where this scientist apparently swerved off the street to avoid a large dog dashing across the road in front of his car and hit a tree hard enough to wreck that vehicle and kill its driver.

It all lead to Bruce darkly brooding to himself in his civilian identity at one of the family manor's sitting rooms. The events of the last few weeks ever since the Joker's death (and the resulting city-wide celebration) had been most odd. One after the other, Batman's adversaries were dying off or ceasing fully their criminal careers. The few opportunities to speak with the survivors usually resulted in them stubbornly refusing to explain these peculiar actions to a costumed vigilante. Threats didn't work either, even when Ace added his own intimidating growl. For some reason, bringing along his dog during this did nothing except making such former soundrels abruptly bursting into real tears. Which did nothing but make everyone concerned extremely embarrassed. And they still wouldn't talk!

Of course, there was one individual he hadn't been able to find, but he'd track her down in due time-

"Master Wayne?" murmured Alfred after materializing by a startled Bruce in his armchair. Dammit, he was Batman! Nobody sneaked up on him! Except for Alfred, Bruce had to admit.

Bruce grumpily replied, "What?"

Holding out a blank white envelope in one gloved hand, this gentleman's gentleman mentally ticked off another victory over someone who needed to learn pride goeth before a fall. In his crisp British accent, Alfred announced, "I found this with a letter inside placed before the front door. It wasn't there a few hours ago, which is when I collected the regular mail. As per your instructions, all precautions against poisons and germ attacks were carried out and neither of these were discovered on the envelope. The same was done for the letter with corresponding results, though I naturally made sure not to read the letter."

Both surprised and wary at such news, Bruce accepted the envelope and extricated the letter it contained. Unfolding the single sheet of paper, the last living Wayne read in a flowing, feminine hand:

Bruce, our love-hate relationship with each other, you as Batman and myself as Catwoman, it's been delightful, but I must tell you we've now come to a parting of the ways.

The whole basis of the connection we had was due to a very simple reason: Opposites attract.

I'm a woman, you're a man. You're a hero, I'm a rogue. I steal anything which catches my eye, you catch thieves. And so on.

However, I've met a very unique person who fits this raison d'être far better than you ever could. As a consequence, I'll be leaving Gotham with him. It's highly doubtful either of us shall ever return, so I thought it only proper to bid you a fond farewell.

Please don't attempt to find us. You wouldn't recognize our new identities, anyway, once we visited an extremely discreet mage of my acquaintance. Fortunately, Xander's sheer impressiveness carried over in his bodily transformation, though I would've stayed with him regardless of whatever failure which might've occurred. Yes, quite immoral of me, but I don't care!

Oh. Perhaps you might not understand, dear Bruce?

Well, think of this: Cat/dog.

Kisses,

Selina

Alfred Pennyworth watched with increasing alarm at how Master Bruce's face turned white, then brick-red, and back to pasty paleness while reading the letter. In an extremely strangled voice, a Gotham scion inquired, "Alfred, have you seen Ace today?"

The butler asked this couldn't help but take a moment to mull it over. He responded with a hint of bewilderment in his own tone, "Not since last night, sir, down in the cave. Why? Is the dog missing-?"

Interrupting his father-figure, Bruce Wayne said with absolute inflexibility, "Never mind. Just two things. First, and tell Dick this as soon as you can, none of us will ever mention again Ace the Bat-Hound. Second, got to the wine cellar and collect a dozen bottles of the port my father laid down the day I was born. I'm going to get as drunk as possible, starting when you get back here with them."

"Very good, sir," calmly responded Alfred. It was only when he was out of the sitting room that this butler had a moment of pity for anyone stupid enough to violate the law even in the most minor detail throughout Gotham City for the next week or so, when a hungover Batman went on his relentless rampage against crime.