Author's notes: This one was a bit harder for me to write, since the account of the source material seems to have been deleted, but I knew that I had to write it! I'm not entirely sure if this has been done before, but there's a first for everything!

The 'Bad Boy and Princess AU' has hands down been one of the more tame in that it isn't as angst-filled as the other AUs that I've come across, and the fan art for it is cute.

To those that have read and commented on my previous work: Thank you! It makes me happy to know that you enjoy what I write, and I'm aiming to keep moving forward! As always, comments and critiques are greatly appreciated!

Disclaimer: Star Vs The Forces of Evil belongs to Daron Nefcy

Today just wasn't his day.

Marco Diaz had gone through a few rough patches in his life. A good majority of his childhood had been spent cultivating him into the person that he was now: a self-proclaimed 'bad boy' that made sure that everyone around him knew it. He'd even taken up boxing to further prove his point that he was 'tough', much to the ire of his parents. Often he'd be told that it should 'only be used in self-defense,' and it had been so far. It was the only way that he could continue getting lessons, and it wasn't like he was about to disobey his parents; even he had morals.

But for some odd reason, today had decided to turn the boy's life upside down. A foreign exchange student had enrolled in his school today, and it was his job to take care of her and show her around. It wouldn't have been a problem, had she been a normal human being. Star Butterfly, the new 'exchange student,' was supposedly a princess from another dimension. He'd laughed when she first told him, finding it so outlandish that no one in their right mind would believe her, but across the course of the day Marco had found every claim to be true; she even had a magic wand! And the best part of it was that he was forced to live with her throughout the duration of her stay on Earth.

Currently, he was standing outside of a convenience store, soaking wet with a scowl planted firmly on his face because of a small, floating rain cloud that was just a few inches above his head, courtesy of his new housemate. He'd gone in for a quick snack, only to be kicked out because he was 'making the workplace unsafe.'

"Hey, hey! You forgot my refill!" A deep sigh escaped Marco's mouth at the retreating form of a man who had just left the building, and he threw away his cup into a nearby trashcan. Irritation had been gradually welling up inside of him after Star's appearance, and it wouldn't be too long before he reached his breaking point. Taking a deep breath in an attempt to calm himself, Marco turned around, not even a step towards entering the convenience store when he was face to face with the source of his problems.

He let out a surprised yell, taking a step back and almost falling over, but managed to catch himself at the last second. Marco's eyebrows furrowed as he formulated what he was going to say in his mind; he was going to get his point across that she needed to leave. Right as he was going to open his mouth to speak, however, the princess held her wand out towards the rain cloud above his head, and it quickly disappeared in a puff of magic.

"Look," she said, averting eye contact and holding onto her arm as she spoke, "I admit that I'm about as happy as you are about the current situation, but I never really had a say in the matter. And you never really had a choice about having to take care of me, either." A beat of silence passed between the two of them before Star let out a quiet sigh. "I apologize for what I've done today. I suppose I'll just have to find another family, then…"

Whatever Marco had been planning on saying suddenly died in his throat as he took in the princess's words. As exasperated as he was by Star's antics, he just couldn't find it within himself to get angry at her. The guilt was written on her face, and he could tell that what she had said was genuine.

Marco's features softened a bit as he reached a hand out towards the princess, but it quickly dissipated, his face morphing into a look of shock as he looked over her shoulder. "P-Princess!"

Confused by the sudden change in Marco's voice, Star turned around, her eyes widening at the sight before her.

A large group of monsters stood before the duo. Some of them were simple in design, and others looked completely outlandish; a few of them had an extra limb or two, driving the point home that whatever they were, they certainly weren't human. Glares and evil smiles could be seen on their faces, and at the front of the group, wrapped in a simple cloak and wearing a skull of sorts on their head, was the group's leader.

"Star Butterfly." The nasally voice that had come out of the short monster's mouth was incredibly annoying, and it was further accentuated by the laughter that soon followed.

"Ludo! What are you doing here?" A look of distaste marked Star's features as she took a step back, inching her way behind the equally confused boy next to her. How had he even found out where she was?

"That doesn't matter. The important thing right now is for you," he said, pointing towards the girl before holding his hand out, "to give me the wand."

The princess barely withheld scoffing at the leader and his cohorts as she brought her hands behind her back, obstructing the wand from view. "You know full well that I will do no such thing. I have no idea how you found me, but I would suggest that you leave."

More laughter filled the air as Ludo propped his hands onto his knees, bent forward slightly from the absurdity of the princess's command. "Really?" Wiping a stray tear from the corner of his eye, the monster straightened up to his full height, which even then was still short, as he continued, "I don't think that you're in any position to argue, Star Butterfly. Men, grab that wand!"

All of the monsters let out a short yell as they advanced on the two, intent on carrying out their master's order. With a group like theirs against only the two of them, the monsters figured that they'd have the wand in their possession within minutes.

The calm and collected facade that Star had worn quickly crumbled as the group of monsters rushed her and the boy who was currently acting as her shield. Something deep within her was crying desperately for her to use the artifact she was currently holding, but her body refused to act. Closing her eyes, Star instead resigned herself to do nothing, opening her mouth to tell Marco to run while he still could, when a pained cry entered her ears.

One of the monsters was sprawled out on the ground when the princess opened her eyes, holding their stomach as tightly as they could. Looking up, Star was surprised to find Marco standing right in front of her, holding his clenched fists in front of his face.

"Keep your hands off of her. You want her wand so badly? You're going to have to get through me, first."

There was an unwavering confidence in Marco's voice as he stared the monsters down, lightly bobbing his head back and forth to a rhythm only he was keeping track of. While he didn't really know the dimensional princess all too well, it didn't take much to figure out that this 'Ludo' person wasn't exactly a friend of her's. As soon the monsters rushed forward, his boxing instincts kicked in, and the end result seemed to work out in his favor.

Having halted in their advance when one of their own had gone down, the monsters looked at the boy standing in front of them before looking at each other, confusion and unease evident in their hesitance to move forward. A sharp 'What are you doing?! Get him!' from their leader snapped the group out of their trance.

Star could only stared wide-eyed in awe as Marco advanced forward to meet the monsters. Everything he did showed just how proficient he was at fighting; he made sure to keep light on his feet, constantly moving around and avoiding whatever attack was thrown at him; his punches were quick, precise, and powerful, sending a few of the monsters a couple of steps back or onto the ground. After downing yet another monster, Star found herself wondering if there were more people who fought like Marco did here on Earth.

As hard as he tried to fend off the attacks that kept coming his way, Marco was still human. He was starting to breathe a bit harder than usual, and his muscles were beginning to ache as the fight dragged on. Ducking underneath another punch, Marco failed to avoid the next one that followed, hitting him on his side and forcing him back a bit. Using this small act of vulnerability as their chance, a few of the monsters moved past the boy and headed straight for the girl who had been watching the whole thing from a distance.

Letting out a grunt as he his side, Marco was forced to continue dodging as he was moved further away from the person that he was trying to protect. "Princess! Use your wand!"

"I can't! A proper princess must-" A small squeak interrupted her as Star barely managed to avoid being grabbed by one of the larger monsters. "A proper princess must wait for someone to save her if she is in a state of danger!"

"Look, princess," he sighed, "I'm not going to sit here and say that I understand what you're going through. But you've got to understand that-" Before he could finish what he was going to say, Marco found himself being tackled and pushed to the ground, hissing a bit as two monsters pinned him down.

"You've got to understand that there won't always be a 'Prince Charming' to come and save you," he said, trying to wring his arms free of the monsters' combined hold on him. "You can't seriously expect me to believe that you're just going to sit around and do nothing, right? If you've got the power to help yourself, then use it!"

The boy's words echoed in Star's mind as she spun around a monster and their attempt to grab her. Using her wand was absolutely forbidden until she was ready to control it; everything that she had been taught was in preparation for her inevitable role as the future queen of Mewni. What would her parents say if they found that she was using the wand despite their warnings about being careful on Earth?

Preoccupied with her thoughts, Star let out a gasp when a monster grabbed her hand, using the other to try and pry the wand from her grasp. She didn't know whether to scream or rip her hand out of the monster's grasp.

What was she supposed to do?

Star's mind was torn between thoughts of her parents, the endangerment of Marco's life, Ludo and his minions, and doing something to get them out of their current predicament, and everything suddenly crashed down onto her. Feeling a wave of pain pass through her head, Star let out a loud yell as she wrenched her hand away from the monster.

The same feeling from before spread like wildfire throughout her body as she curled forward, her current aggressor now taking a few steps back out of shock. The only thing running through the princess's mind at the moment were two things: She needed to take matters into her own hands, and her parents weren't on Earth.

Eyes aglow with a newfound determination, Star Butterfly stood up to her full height, wand raised into the air. A few of the monsters looked over at the Princess, a slight chill running down their spines at the sudden look the formerly helpless princess was giving them. Even Marco, who had finally managed to free himself from the monsters' grapple and was back onto his feet, felt a bit uneasy at Star's sudden change in personality.

"That is enough! You will let Marco go, and leave us alone!" A bright light began pulsating from the face of the wand, picking up its speed as Star held it out towards the group. "Mega Narwhal Blast!"

The light suddenly burst forth from the wand, forcing those looking at it to shield their eyes for a few seconds. When it died down, the monsters frantically looked around, preparing themselves for whatever sort of attack the princess had thrown at them. When they turned their attention skyward, all they could do was gape as small narwhals rained down from the sky.

Once the dust settled, all of the monsters that Ludo had brought with him were incapacitated, lying down in the dirt and cradling their injuries or trying to free themselves from the mass of narwhals that lay on top of them. It took a few minutes for the group to get back onto their feet, groaning and moaning all the while, before Ludo took a pair of strange looking scissors out of his pocket and cut at the air, opening a large portal that presumably led back to wherever it was that they had come from.

"Come on, get through the portal! Losers, all of you! How could you all lose to the two of them?!" Once the final monster of the group stepped through the portal, Ludo turned towards the duo, a frown planted on his face. "Mark my words, Star Butterfly, that wand will be mine! Just you wait-" The monster was shoved through the portal before he had a chance to finish his little spiel, and with a quick 'pop,' the portal disappeared, leaving Star and Marco alone.

Looking down at his clothes, Marco let out a small sigh as he dusted himself off. The fight had left him with dirty clothing - there was a small rip in his favorite hoodie! - and a few bruises from the times that he had been hit or grabbed. Once he made sure that his appearance was acceptable, Marco walked over to Star, a faint grin visible on his face.

"And here I am, thinking that I'd have to do all of the heavy lifting. " Laughter filled the air as Marco Diaz gave the princess a light nudge on the shoulder. "Not bad, princess. Not bad at all."

"We were quite the force to be reckoned with, weren't we?" A small smile was seen on the princess's face as she looked at the boy in front of her. The gratitude that she held towards Marco was immense, and she wasn't sure how she could repay him for what he had done. However, a particular thought did cross her mind after a few moments of thinking, and the smile quickly disappeared from her face.

"Well, I suppose that I should inform your parents and… pack my things." Star's demeanor dimmed as she slouched forward a bit, turned around and began to walk off. This was the right choice; she'd already caused the boy enough trouble already, and after tonight, she was sure that Marco wanted nothing else to do with her ever again.

Watching as she began to walk off, Marco let out a sigh before catching up to her and placing a hand on Star's shoulder. "Princess," he started before pausing for a moment, shaking his head. "No... Star. I don't want you to leave. You should stay with us. Who else is going to help you out if those guys show up again?"

Disregarding the fact that she had just been attacked by a horde of monsters not a few minutes prior, Star looked at Marco as if he had said the most ridiculous thing she'd ever heard. "Really? You mean it?"

A surge of overwhelming emotion filled her chest as Star turned around and wrapped her arms around Marco, much to the boy's surprise. A beat of silence passed by before Marco returned the gesture, smiling softly as he gently pat the princess on the back. Once they separated themselves from each other, the two walked off, talking about what the future held in store for them now that it had been decided that Star would be staying with the Diaz's.

Maybe today wasn't so bad after all.