Just so we're clear, this story isn't set in the same canon as my other Sonic-related works. This one is meant to be in the mainline canon, even though it's a fanfic.
The sleek, metallic hallways were dimly lit, cloaked in an almost eerie silence, save for a lone set of footsteps. On a good day, Dr. Eggman's base would be loud and abuzz with the sounds of all sorts of gadgetry, whether it be the machines that assisted in the production of his robot armies, the computers on which he wrote down and stored his evil plans, or even the technology he used to make his leisure time even more leisurely. Today, however, seemed to be a bad day, as shown by the constant grumbles the doctor released as he headed into the central computer room.
The automatic door whooshed open as he approached, and the lights inside the room instantly switched on, revealing a large number of futuristic computers with brightly colored screens, arranged haphazardly around the multiple levels of the massive room, and all accessible via a comfy hover chair. But now was not the time to stare in awe at what he had created, for Eggman felt too forlorn as he immediately slumped into the aforementioned chair, resting his head in his calloused hands, and seemingly ignoring his two lackeys as they tidied up the room.
"Yo, Boss! Wanna test out the new massage feature I installed in that chair?" Cubot asked, his cheery mood clashing with his surroundings. "You look like you could use it."
"Don't worry, I helped him do it, knowing he'd screw it up otherwise," Orbot butt in, but they both went ignored. Usually, Eggman would reply to anything they said with a snarky or insensitive comment, but he remained dead silent. "Er, boss? Are you alright?"
"I just can't believe my streak of bad luck when it comes to trouncing that obnoxious little hedgehog! I've tried harnessing the power of all god-like beings in this universe, and not even they stood a chance!" the doctor finally blurted out.
"Maybe it's a sign you should abandon the whole monster-of-the-week formula- ow!" Cubot was silenced with a karate chop to the head from his partner.
"Ignore him. Look, the important thing here is to not give up. There has to be someone out there powerful enough to annihilate him," Orbot suggested.
"Like who? Like I said, I've allied with every single strong being in this universe: Chaos, Dark Gaia, the Wisps, the Deadly Six… why, I've even tried siphoning the energy from the planet itself! And don't even get me started on Knuckles and Shadow; I tried using them too, and now they're all buddy-buddy with that blue durian!" Eggman explained.
"Maybe you could whip out Metal Sonic again?" Cubot shrugged.
"Or if you're out of options in this world, perhaps you could try another?" Orbot added.
"Hmm, those are both really awesome ideas! Glad I thought of 'em!" Eggman's eyes suddenly lit up behind his shades, a grin peeking out from under his wild mustache.
Both the robots rolled their eyes as they followed their boss to the mechanic room. Leave it to him to never give them any credit for all the years of assistance they'd given him.
Before everyone knew it, they were standing before a massive, ring-like metal structure, painted gold and resting on a stand, adorned with a series of buttons and switches. Such a device would've taken any other scientist years to perfect, but thanks to Dr. Eggman's IQ of 300, he knocked it out in just a couple of hours. Then again, it also helped that he had a whole army of robots to assist him. Satisfied with his work, Eggman sat back in his vibrating chair, staring in awe at his newest creation as he munched on a grinder.
"Wow, never thought I'd say this, but great work, bots!" he nodded, popping the last bite into his mouth as he stood up. "Heh heh, now all I have to do is turn this thing on and figure out where to start pulling my new minions from…"
"Shouldn't you think of a clever name for this thing, first?" Cubot asked.
"No time for that! I've got a hedgehog to trash!"
With that, the trio stood around the new machine as the doctor flipped the on switch, causing what looked to be a swirling portal to an unknown location to appear inside the ring. Purple, just like most of the rays and other devices Eggman had built over the years.
"Hmmm, Wumpa Islands? Hyrule? Skyworld? Planet Popstar? Wow, these people must've had a lot of fun naming their homes… ooh, Mushroom Kingdom? Well, if it's anything like Mushroom Hill Zone, I'm sure I'll love it," Eggman grinned again as the portal opened a bit, revealing a scene taking place inside a medieval castle filled with lava and chains. "Whoa, what? Talk about false advertising! I'm not seeing a single mushroom in there!"
"Forget that, sir! What in Biolizard's name is that thing?!" Orbot pointed a trembling hand at the creature who appeared on the other side.
"And why's that castle covered in his likeness?" Cubot shivered as well, maintaining a death grip on his sidekick.
The being in question looked to be a menacingly large, turtle-like monster with scaly yellow skin and crazed red hair to match his demonic eyes. His arms and neck were adorned with spiked gauntlets, with horns on his head and spikes on his green shell. Stomping into the center of the round, black platform, he let out a long, fearsome roar. Behind him was a set of bars embedded into the brick wall, with a blond human woman in a pink gown trapped behind them.
"Whoa-ho-ho! First try, huh? Well, looks like my luck is about to change!" Eggman cheered, already parked in front of the portal with a bowl of caramel corn. "Oh, but who is that guy?"
Leaping onto the same platform and landing in front of the turtle-like being was a rather stout, soft-spoken man in blue overalls over a red shirt, with a matching Gatsby cap that contained an M on the front. Looking up from where he landed, he shot a death glare at the beast, before backflipping off the ground and landing in a boxing stance.
"I take it he's another one of your potential minions?" Orbot asked.
"Tch, I hope not. He looks a little too wimpy for my tastes… although he does have a pretty nice mustache… eh, whatever. Looks like they're about to fight, so let's see what this monster can do."
"Bwahaha, y'know I shouldn't be surprised to see you made it this far, Mario. Nice to see that even after over twenty years of being my nemesis, you haven't gotten soft on me," the turtle taunted.
Mario said nothing, but maintained his no-nonsense demeanor, coming in stark contrast to his bright, childish appearance.
"Well I've got news for you too, plumber: I ain't getting soft either! In fact, I've been training a lot since the Delfino Plaza incident, so you might wanna be on your guard! Especially without that dumb super soaker to save you!"
Releasing one last roar, the giant turtle leapt high into the air, demonstrating a deceptive amount of mobility. Mario ran forward a bit and somersaulted along the ground to avoid the stomp attack, but was not prepared for his nemesis to shake the platform upon landing, catapulting him towards one of the walls. The turtle attempted to nail him while he was stunned and flailing by spewing a stream of fire-breath, but Mario quickly caught onto this and kicked off the wall, launching himself above the projectile and front-flipping back onto the platform. His foe wasted no time in throwing out a swift punch, but this was counteracted when he launched a dropkick at his oncoming fist, smacking him in the face and knocking him onto his back. Mario capitalized on the opportunity by rushing over and grabbing his tail, spinning him around faster and faster with his deceptively high physical strength.
However, he suddenly felt the tail slipping out of his grasp as the turtle tucked into his spine-covered shell, spinning around like a top and almost hovering in the air.
"Mwahahahaha! You thought that move was a Smash Bros.-exclusive, eh? Well I hate to break it to ya', but it's not!" he teased.
Without saying another word, he remained inside his carapace and hurtled towards Mario, who sidestepped out of the way, allowing him to accidentally slide off the platform and plunge into the lava. It didn't take long for the shell to quickly spring back up, smoke leaking out of its limb holes as it continued to spin around, albeit in a disoriented and aimless fashion.
"Whoa!" Mario barely managed to evade this with a series of jumps and cartwheels, and remained silent as his enemy untucked his burned-up body from his shell with a pained roar.
"Grrr, that was a dirty trick!" the turtle grumbled. "Fine then, I see how it is. Well I can fight dirty too!"
With that, he lurched forward in the blink of an eye and belly-flopped down onto his much smaller nemesis. Coiling his burly arms around his torso, he leapt high into the air and flipped around a few times, before drawing back a scaly fist.
"Mamma mia!" Mario yelped, before he was punched hard in the gut and plummeted back onto the platform. "Oof!"
But he didn't have much time to recover, as he quickly noticed his adversary had curled back into his shell and was falling right towards him, spikes aimed downwards. Mario quickly slid forward and bolted upright, managing to leap off the platform before his foe shattered it into smaller chunks, drifting around the pool of lava. He barely managed to land on one of them, but quickly found himself having to leap between them in order to dodge the onslaught of fireballs that were spat at him, which destroyed the remaining portions of the platform. Once Mario reached the final chunk, he had no choice but to leap towards his foe, barely managing to dodge the last fireball, before knocking him away with a strong dive kick to the nose, ending the combo with a flip kick.
The massive turtle was sent crashing into the wall, breaking down the bars where the blond woman was being kept prisoner, before he fell back into the lava. He came back up to doggy-paddle at the surface, but was quickly pinned down by several chunks of the wall that fell onto him. With his foe vanquished, Mario took a few seconds to catch his breath.
"So long, eh Bowser," he quipped, before wasting no more time and hopping over to the alcove in the wall, scooping up the princess and using his parkour skills to kick off the walls and escape the room.
"Oh, so that's his name?" Orbot pondered. "Doesn't sound very menacing…"
"What?! No! Nooo! How could he lose to that man?!" Eggman screamed in rage, angrily tossing his popcorn after the fight ended, only for it to accidentally fly into the portal. "Whoops…"
"Sounds like he's not quite what we're looking for," Orbot replied.
"N-No, nonsense! Sure, that turtle got his butt kicked, but it's nothing that can't be prevented. Plus, his abilities are too impressive to just overlook."
"Oh boy, here we go…"
"Shut up! Now, let's go rescue that brute before he's cooked alive," Eggman stood up and was about to step into the portal, but was caught off guard as it started to flicker. "What the- Cubot!"
"Huh?" Cubot stopped what he was doing, only to suddenly get electrocuted by the outlet he was standing near.
"You imbecile! What made you think it was a good idea to mop right by an outlet?!"
"Er, I-I was just trying to clean up the grease stains from all that work we just did! I didn't mean to cause any trouble!"
Before anything more could be said, a surge of purple electricity slipped out of the portal device and through the plug that was powering it, before things quickly ramped up.
That same burst of energy traveled through telephone wires and electrical grids throughout the world, before it eventually became too powerful and exploded, forming several smaller purple portals all over the planet. One of which happened to spawn right next to the emerald shrine on Angel Island, quickly alerting the red echidna who was sleeping right next to it.
"What the heck? What's going on?!" Knuckles shrieked. "Hey, give that back!"
Despite his admirable strength, he wasn't able to stop the portal from completely engulfing the Master Emerald. Instead, when he summoned every ounce of raw power he had, he ended up ripping the emerald in half, both halved instantly shattering and getting blown away in the process. Half of the countless shards ended up flying into the Mushroom Kingdom, much to the guardian's ire.
"Aw, darn it! And to think I've managed to go several years without this thing getting stolen or broken…"
Back at the base, Eggman, Orbot, and Cubot had been hiding behind a fold-up table, nervously peeking out as they watched the portal machine tremble for a good while. Eventually, it finally stopped humming and reverted to a more stable condition, Mario's world still visible on the other side. The doctor nervously stepped back into the open and examined the machine for a bit.
"Welp, looks pretty stable to me. Consider yourself lucky, Cubot, because you just saved yourself a good disassembling," he barked, prompting his minion to cower. "Orbot, get the Eggmobile ready. We're going to the Mushroom Kingdom!"
"Right away, sir!" Orbot scurried off.
Meanwhile, a deafening roar of agony echoed throughout the halls of Bowser's castle, accompanied by a few isolated sounds of cold breezes and crackling ice. The turtle that Mario had beaten in the previous fight was resting on top of a table that was built with a design that complimented the rest of the castle around him, sporting two black eyes and bandages over various parts of his body.
"C'mon Dad, be strong!" whined a younger, smaller turtle who resembled him, sporting a bib with drawn-on fangs.
"Junior's right, Master," squawked an elderly, bespectacled turtle with a slouch, dressed in a blue warlock robe. "I know it might hurt, but I'm afraid these ice flowers are the only way to help with those burns."
"Rraagghh, darn you, Kamek! Can't you just use magic to numb the pain or something?" Bowser groaned.
"Well, last I checked, you're allergic to Super Mushrooms," Kamek snarked. "And if you're talking about my magic… well, I'm afraid it isn't as potent as it used to be."
"Grrr, of all times to play the old man card…"
"Speaking of old men, who the heck is that?" Bowser Jr. pointed a clawed finger at Eggman, wandering into the throne room alongside Orbot and Cubot.
"Yeesh, talk about a dump! Then again, maybe I shouldn't judge, given the fighting prowess that apparently comes out of here," the doctor took his jabs at the castle, quickly met with some suspicious glares from the koopas before him.
"Ey, who do you think you are barging into my lair?!" Bowser abruptly leapt to his feet, clenching his fists and seemingly ignoring the pain remaining in his body.
"The name is Ivo Robotnik, though most people these days call me Dr. Eggman," Eggman boasted with an open hand to his chest, eliciting some chuckles from Junior and Kamek.
"I'm Cubot, and the red guy next to me is named Orbot," Cubot introduced.
"Nobody cares! Now it just so happens that I was working on a machine that could transport beings across universes, and I managed to witness you fighting this… Mario character earlier."
"Don't remind me," Bowser growled, folding his arms. "For a guy who's so portly and has the personality of a cardboard box, he sure can hold his own. And what's with his voice anyway? The man's clearly in his thirties, yet he always sounds like someone kicked him."
"Yes, well regardless of the outcome, I was rather impressed with the abilities you displayed during the battle, and I feel you could be a valuable asset to my evil schemes."
"Hey now, let's get one thing straight: I'm all for evil, but I don't play asset to anyone! Either 50-50, 70-30 in my favor, or no alliance at all!"
"Fine, fine, 50-50. We shake on this, and I'll give you access to my tech. I can upgrade your forces, strengthen your castle, and help you stand a better chance at whatever your sinister goals are. I also have some highly advanced healthcare that'll help patch you right up."
"Huh, you drive a hard bargain, dude," Bowser stalled a bit, taking a few seconds to think the offer over. "Kamek, cancel that princess kidnapping! We're gonna delay it for a bit, while we do some beefing up."
"As you wish, sire," Kamek bowed, summoning a broomstick and flying out of the room.
"Eggman, you got yourself a deal."
"Glad to hear it, Bowser," Eggman grinned, shaking the Koopa King's hand. "So, about this princess kidnapping. Who is she, and what's your motive?"
"She's only the most stunning female outside of my own species I've ever laid eyes upon," Bowser explained.
"Wait, your own species? Oh, so I do have a mom," Bowser Jr. chimed in, but went ignored.
"I mainly kidnap her as a power move, giving me legal authority over the Mushroom Kingdom, but it's also a way to lure Mario into my traps."
"…which always fail," Eggman nodded.
"Hey, I've succeeded a few times!"
"Well that aside, my goal is to take over my home dimension by harnessing the power of beings even stronger than I am, while also trying to prevent an annoying blue hedgehog from thwarting me."
"And you choose a different one to enslave every single time? With no repetition or consistency?"
"Pretty much. I like to spice things up!"
"Huh, I never thought about it like that before…" Bowser paused again. "…we're really not so different!"