A/N: While I'm not a fan of fanfics literally writing out movies, shows, etc word for word, the few exceptions I would allow if it's on stuff I love. Ergo, this.

I only own my OC; aka my self insert, which is inspired from previous iterations from my stories Cyber Chase and I Love You Too Much but with a new origin/powers as OC me has literally been over a decade in the works.

That and this crossover makes me want Ben 10 mature content so bad~!

Anyway, for anyone reading this, I hope you enjoy.

Rex thought it would be a regular day.

Starting out an early morning by just riding his Rex Ride some distance away from base, testing his speed and trying to break his current record.

And that's when the rift happened.

A small one, shimmering blue light rays coming out of it followed by a form falling out of it before it vanished like it was never there. From high up in the sky.

"Okay. That's new." Rex spoke like it was part of the norm that was his hectic, strange life. He skidded to a stop before he changed his build. The orange hover motorbike morphed back into his lower legs before the Boogie Pack took root on his back, adjusting his goggles before the wide orange turbine wings thrummed with energy as he pushed off the ground.

Flying at high speed, he easily zoomed up to catch the falling person in his arms. He grunted as he adjusted his hold on them when he looked down to see they were a she.

He landed safe back on ground, undid his build, and got on his knees as he held her in his lap. He pulled his goggle off his eyes and back on top his head, letting his bare eyes look over the unconscious gal.

"Uh Doc? You might not believe me when I tell you this. But we've dealt with stranger things before … though none like this."

To the Super Secret Spy hideout in the dam they go!

000

They all heard moaning as she was starting to come to.

Opening her fuzzy brown eyes, she blinked several times to clear the blurriness as they spoke.

"She's coming to." Holiday hurried over.

"Careful. Keep your guards up." Six's shades gleamed as he kept a hand to the hilt of his sword.

"Eh, not too shabby looking." Bobo gruffly commented.

"Dude, restraint." Rex grabbed the back of the chimpanzee's collar to keep him from making a move.

"Mmm … huh? W – Where am I?" The awakening young lady tried moving only for Holiday to hold her gently by the shoulders as she made her lie back down in their giant tube aka make-shit medical bed.

"Easy now. Don't rush yourself." Holiday gently cautioned.

"W – Where am I? Where am I now? How long was I out?" She took her time for her senses to clear enough to see it all.

"Since I caught you falling out of the sky." When her sleepiness faded enough for adrenaline to kick in to see two adults, a teen a bit older than her who was the closest to her to reply, and a monkey in a fedora and eyepatch to make her jump up on her bum and scoot as far as she could in the open tube. "Whoa, whoa. It's okay. We're not gonna hurt you."

"There is the possibility she could be an undercover agent for Providence." Six warned them, face narrowed.

"Unless they invented a device to create literal rifts in space just to send one of their cronies to attack us when they could have just come through the hanger bay, I'm not so sure. Then again, we deal with all things sci-fi in our profession. Still … " Rex explained before turning to the stunned girl.

Dark brown hair in a loose ponytail, fair skin with a mole below her right eye and a faint scar on her forehead, and brown eyes to pair. She was tall, skinny, and teemed with the impression of someone who is sensitive, shy, and … sweet. He could see it on her face, in her nervous form as she hugged herself to shield herself from unknown harm, and the worry in her eyes.

"She's not a threat. Not to us."

"And you know this how?" Six dare ask.

"A gut feeling." Rex's face turned for his eyes to lock on Six's; he could imagine seeing them through those shades. Six's guarded form deflated down somewhat, nodding in silent understanding. If his kid chose to believe in what he feels inside, then he would side with him. Rex smiled, thankful, before turning back to the girl, squatting down to meet her gaze, smiling gently. "I'm Rex. This is Holiday, Six, and Bobo." He pointed out each one of them. "What's your name?"

"I …" A blossom tint rose to her cheeks, making her flustered state more noticeable as she averted her eyes shyly, "My full first name makes it hard for newcomers to pronounce and it's embarrassing for all involved. Just … you can call me G."

Rex chuckled internally at the cute sight. "Just the letter?" Rex received a nod in return. "Huh. Okay. It's nice to meet you, G." Rex presented his gloved hand out to her, wanting a handshake.

She slightly gaped at how casual he was treating her before her lips relaxed into a elated smile, reaching her hand out to join his. They shake on it.

"So …" Rex drawled out, "Whose gonna tell White Knight about our new guest?"

"You brought her here." Six dryly pointed out.

"I have to run some more tests on her just to make sure." Holiday easily reasoned.

"Good luck to ya, pal." Bobo patted on Rex's back.

Rex slumped in defeat "Gee, thanks."

000

Braving through White Knight's lecture and instructions to keep an eye on their new guest before dismissing him to work on his own tasks wasn't as bad as he expected it to be; though he was used to White being who he is by now especially after traveling half a year into this new present age. Using Holiday's make-shit bedroom as her temporary room was fortunate, due to Holiday having to go over the data collected on that rift from before but so far, it was kind of a hassle. Especially since all they had to work with were prototype tools; Holiday still wished they were tested and functioned well.

The room had a view of the hanger bay above the big bed where he would later have to practice sparring with Six in to sharpen his apparent sloppy shape; according to his mentor. As he opened the door for G to walk in first and watched her look around the tidy small room, Rex's calm demeanor didn't stop the frown showing up on his face after what Holiday said.

After she cleared G with a clean bill of health and asked her to wait outside for Rex while she briefed him on private matters, Doc went straight into it as soon as the door automatically closed shut.

"She came through that rift with no nanites in her."

"Hold on. I thought White Knight was the exception to the nanite issue."

"It's not just that. Look at this." Holiday typed keys on the board and pulled up on her machines screen were an outline of a body giving off many statistics, vitals, the works. "Our scanners picked up the rift you spoke of. She gives off a similar signature to it."

"So … you sayin' she has powers similar to Breach's? She can create her own rifts? Seriously!? That would be so cool …" Rex looked amazed until it started to droop " … If not for the fact that it may not point to good signs if it were used against us."

"Six has reason for us to keep our guard up. With Providence after us, we have to be careful. Still, she doesn't seem like the ferocious type. Just … keep an eye on her. Until we know what to do going forward."

He saluted jokingly, "Yes, ma'am!"

Which brings him to right now.

"So …" he awkwardly approached her as she fell back on the bed and sighed at how comfy the mattress and sheets were; sinking into the plush surface, " … how you feelin'?"

"Fine. Sleepy," she proved to be true by yawning in her palm, "But fine."

"Good." Rex pulled up the only chair in the room by the bedside and sat down, crossing one leg over the other and folding his arms across his chest before leaning down to give her a suspicious gaze, "So how much did you hear?"

Her closed eyelids shot open, angling her head to face him with surprised marvel, "How …?"

"I spotted the shadow your feet gave off right on the other side of the door."

"Oh." She quickly grabbed one of the pillows buried beneath her head to bring it up front as a shield as she shrunk back a bit.

"I'm not mad or anything. But … is everything Holiday told me true? Did you make that rift?"

Her brown eyes peaking over the pillow gazed at him, contemplating her course of action next. Her tense expression then softened, pulling the pillow down to embrace it as she rolled onto her side to fully face him. "Yeah … I did."

"Is that your EVO ability?"

"EVO?"

"Exponentially Variegated Organism."

"I know what an EVO is. And no, I'm not one. I'm …" She bit her bottom lip, chewing on it a bit, before releasing it and letting out a resigned breath. "I'm half human, half … cosmic."

Rex titled his head to the side, brow raised and taken back somewhat "Cosmic?"

"I … I'm not from around here."

"Well, my team are looking you up in the databases we can access. It'll take some time but when we get your info, we can transport you back home – "

"It's fruitless effort." She curled in on herself, pressing her cheek against the pillow as she nervously grinned. "I mean… not from this world. This Earth, anyway."

Rex gave a skeptic look. "So what? You're an alien from outer space?"

"Kinda. More like … a Nephilim."

"A what now?"

"Half human … half angel. That or just half cosmic being."

"Okay. Now you're pulling my leg here."

"Look, I don't blame you for not believing me and suspecting me to have ill intention. I thought it was all ludicrous too and didn't know the truth of it for a long time. I just wrote it all off as me like … I don't know, having supposed meta genes activate or being the lucky, special, chosen one or whatever. But … to put in simpler terms, I am what you call a cosmic entity. Half, anyway. Besides," She rolled to lay on her back, staring at the ceiling, eyes mystified with an amorous gleam, cheeks now tinted red as she dreamily smiled, "My closest friend's more alien than anyone else I know."

"Can you prove it?" The question made her head turn to the side, stunned he would take a chance. "From everything I've seen in my line of work, I'll take a leap of faith and say I'll listen. So, anything else you can do besides making rifts?"

She turned back to the ceiling, listing them off with her fingers "Um … make portals … to other places … I also travel temporarily in my sleep … kinda like astral projecting."

"Seriously?" Now that piqued his interest as he leaned forward, his hands now gripping the edge of the mattress.

She cutely grinned "You believe me now?"

"Well, your powers sound more mystical than scientific … that and I'm bored, just passing the time." Rex mused, grinning bemusedly as his hands went to cup his cheeks with his elbows supported on his knees. "So, can you do it right now?"

"I would. But the thing is … my powers drain me. A lot. The more I use them, the more strain I put on my body. Over the years, they've been growing stronger and my control over them takes time and effort. But … I get easily distracted and my mental control can slip cause of it." G yawned again, this time out loud, adding "Plus, I have this health problem that causes hot flashes so I have to take it easy. Which means," she yawned longer as she rolled over, scooting closer to Rex, "Lots of sleep."

Rex couldn't help the warm chuckle leaving his lips as he chose to sit on the edge of the bed beside her. "So no show and tell, sleeping beauty?" She rested her head against his thigh, nuzzling her cheek like a kitty cat, making Rex's cheeks turn rose red.

Her eyes were drooping as she was already falling asleep. "Mmmh, sorry … b – b …. beloved."

Rex's face flared up brighter. Neither Circe nor the other girls he went out with ever called him that. "B-B-B-Beloved!?"

"Oh …" Her eyes then shot open once again, only now panic flashed on her face as she quickly shot up on her bum. "Oh crap! If I'm gone for too long, he's bound to notice something's wrong and come looking for me. At least, I hope so. But maybe – maybe he'll realize I'm in this parallel world and come charging in, watch a blazing! Oh, that'd be so bad ass~!" Her eyes lite up like stars before their light died out as she became paralyzed with fear. "But that could end up pretty bad collateral damage wise. He always make big time messes when he gets to work." But that expression evaporated, replaced by rosy cheeks and a lovesick grin. "Then again, to see his protective, envious self come barreling towards me with such strong intentions makes me feel all kinds of damn~!" She swooned, feigning fainting noises as she fell back on the bed.

Rex's face contorted between bewildered and bizarre; his mind trying to unravel what the heck just happened. "Um … dare I ask who?"

"My childhood friend slash best friend slash first love slash now current boyfriend."

"Your beloved, as well, I presume?"

"Yeah." She bashfully looked away but then shortly turned back to him with an all knowing tone and gaze, "But if you two ever do meet … it's gonna start out in an all out brawl."

Rex's forehead creased and his eyes showed distaste, "Why do I get the feeling you want to see him kick my ass?"

"Sorry." She covered her mouth to hide her guilty smile, murmuring out, "Not sorry."

Rex pouted, "So not cool."

000

Watching from the glass window view inside the ship where Holiday was tinkering beside her after being invited to watch him work, G's eyes were on Rex and Six sparring all over the hanger floor as Rex brought out the Funchucks to swing behind him only for Six to flip over and land on the other side, drawing his blades.

"You need to pay attention."

"I'll tell you what I need."

"More training? Your swing is getting a little sloppy." Six commented as he easily dodged, blocked and rolled away from all Rex's strikes.

"Not what I was thinking, but thanks for the tip! Two words for you, Six. Theme song!" The Funchucks were replaced with the Punk Busters as Rex back flipped away from the double stab attack from above, landing atop the ship.

"Theme song?"

G fell over from the shake caused by Rex's heavy landing whereas Holiday looked stern "Break my stuff … and I will ruin you." But her warning only made Six smirk, feeling so turned on right now.

"Ooh, he like that." G murmured knowingly, peaking over.

"Things have bee pretty good for me lately. I have a home, friends, family. The only thing I need now is my own theme song." Rex then switched to the Blast Caster; whip lashing at the target but still missing him.

"I got your theme song." Bobo commented before making arm pit sounds.

"I'm serious. Every hero should have a theme song. I've been working on one. Though, you probably won't hear it over the ringing in your ears." As Six jumped up to higher ground, Rex switched to the Slam Cannon, taking in some pavement from the floor to chuck many blasts at a speeding Six when he started singing.

"It started when the nanites when KA-POW upon the scene, transforming all the life n Earth like nothing that you've seen. But there's one lucky hombre that can make and build machines. He's Gen Rex – UGH!"

Rex was finished as Six tackled him when he was distracted, his boot pinned on his chest as he was declared the victor and withdrew his swords "It's … catchy."

"Singing the theme song? Not bad. Too bad it's already kinda taken." G murmured again smiling dreamily, catching Holiday's attention but unaware of it, too caught up in her own mind about a certain someone.

"It's good to see you happy Rex. Just remember that in this word right now, all of those things can be taken away in an instant."

"If that was your attempt at inspiring me Six, you need a little more practice yourself." Rex frowned as Six pulled him up when the alarms started blaring; their yellow lights flashing.

"How quickly can we get to Manhattan?" Holiday asked them, walking down the ramp.

"As quick as we can." Rex stated before spotting over Holiday's shoulder a pair of brown eyes peaking behind the ship's door and getting caught by his, making him smirk, "Assuming we can take one more passenger along for the ride. I am in charge of her, if you can recall."

"Fine. But she stays in the ship." Six sighed as they all hurried onto the ship.

"Thank you~!" G sung out softly before zipping back inside.

"Come on, you gotta admit she's too sweet to not have around." Rex jokingly asked Six who had no comment.

Flash forward – lo and behold, an even bigger rift had formed over Manhattan; a swirling storm of clouds and lighting circulating around it and coming of the big ball ripping through time and space itself.

"What is going on here?"

"Don't know. But I wish I brought my tanning butter."

"Cut the chatter."

"I would, but ripping on Black Knight is the only thing that's keeping me from freaking out. This isn't our usual deal. Just make sure Providence doesn't blast off my butt while I'm off saving theirs!" Rex spoke through their com links pieces as he pulled his goggles to cover his eyes, forming the Boogie Pack and flying on off to the heart of the storm.

As G watched in her seat beside Holiday as Rex flew to it, the scientist spoke.

"Why are you giving me the feeling that you know exactly what's transpiring here? Especially since this rift has a similar signature to yours from earlier today. From the moment Rex found you, you – "

"If you think I had anything to do with this rift, you're wrong. I'm no threat to any of you. I don't want to be. But I can tell you … the second thing that comes out of that rift … is." The look G had on her face and in her eyes showed no deception.

"What does that even – ?"

"So, I smash that?" Rex's voice cut her off. He hesitatingly reaches his hand out to the orb only to be blasted back.

"Coming back around, kid. I think it likes you." Bobo called out with wry humor.

Rex kept swerving in the air to dodge more lightning blasts, "Holiday, what is it!? And where do I hit it!?"

"I don't know. I – wait. I'm picking up bio organic energy inside the event." She alerted them on what her scanners displayed.

"Aaaaaaand … right on schedule!" G announced before apologetically smiling. "Sorry." Then, as quickly as she spoke, a shimmering blue light encased her as she teleport away.

"Wait!" Holiday's cry went on deaf ears. "Dammit."

As Rex formed his Smack Hands to land a punch, his left one was caught by his opponent's right one while his left hand curled into a huge fist, hitting its mark, and making Rex roll backwards through the sky to the park far down below. But Rex was able to form his Punk Busters in time to ensure a safe landing instead of becoming a splat stain on the ground.

A shimmering blue light followed by G appearing out of it nearby, hiding among the trees when she spotted Rex's giant mysterious opponent landed, creating a shock wave of rubble and dust.

"My alien giant," G sighed out amorously at her familiar humanoid dinosaur hero.

"Have anything to say for yourself before I commence with the face stomping?"

"Yeah. You just made a HUMONGOUS mistake!" Humungousaur's towering form stalked menacingly towards a scared looking Rex before he clasped his hands together, raising them high up, then slamming them down.

And thus, the brawl commenced!

A/N: I will say it now.

This story is basically a Heroes United AU with Ben x OC mature content so expect language, swearing, violence and smut galore (like 2 or so chapters of smut).

This is my favorite crossover OF ALL TIME, and reading Rex10: Ultimate Partners by lightningcurse4you really turned me on~! So ... yeah.

I will also be posting this story on my wattpad and quotev profiles but may add a bonus mature chapter to them as I have an idea that I feel shy about putting on here ... IDK yet.

Until next time, later!