So this idea has been in my head ever since I started thinking of my one-shot series of two characters that should meet. And since there is barley any fanfiction about a crossover between Star vs. the Forces of Evil and RWBY, I decided to make a one-shot to show other people it can be done and you can write fanfiction about a crossover between the two shows. This is set between Volume 2 and 3 of RWBY and the episodes "Just Friends" and "Face the Music" of Star vs. the Forces of Evil. The reason I chose Star and Ruby is because there both quirky girls who have pretty big futures ahead of them, and I think it would be fun for Star to go up against some Grimm... Also before I start I want you guys to know that this is my first time writing a Star vs. the Forces of Evil and RWBY fanfiction, so please forgive me if I'm pretty bad at it. I also thought it would be a good exercise for my upcoming Sonic the Hedgehog meets RWBY crossover that will be apart of my Sonic and Shadow universe. My Shadow the Hedgehog meets Attack on Titan story is up and yes it is apart of my universe. Now lets get this story started!

The Butterfly and The Rose

(Ruby POV)

It has just been a few weeks after the White Fang attack on Vale. Many Grimm managed to get their way into the city to cause chaos and destruction, but thanks to the Huntsmen and Huntresses in training with the help of the James Ironwood's army, they wiped the Grimm away from the city. But many Grimm found holes from the subway and manged to get into parts that have not yet been blocked off. The Grimm were starting to make their way back to Vale, but Professor Ozpin is sending the Huntsmen and Huntresses in training to fend them off until the holes were completely fixed. And now Ruby Rose, Huntresses in training is sent off to the Emerald Forest with the rest of her team to eliminate the Grimm from this area. But Team RWBY was sent off to different locations of the Emerald Forest. Dashing through the woods with a streak of rose petals, Ruby Rose saw a Beowolf walking from a distance, she then held out the Crescent Rose from her hand and sliced it's clean head off. As the dead Beowolf disintegrated, Ruby looked up to see four more Beowolf's starring right back at her.

"Did I just kill your friend?" Ruby said, with a hint of fright in her voice as they started to approach her. "If I did, I'm not sorry."

A Beowolf rushed towards her but Ruby turned the Crescent Rose into a rifle and shot the Beowolf many times until it collapsed right in front of her. Another Beowolf swiped at Ruby but Ruby luckily dodged the attack by rolling away. Ruby turned the Crescent Rose back into a scythe and cut through it's back. With the other two Beowlf's rushing towards her at the same time. Ruby towards them both and manged to cut both of them in half with her scythe. As the last of Beowolf's disintegrated Ruby stood catching her breath before she dashed off again to another location to fight off the Grimm. But before she could do so she heard the words yelled, "RAINBOW Fist BLAST!"

Just then, a Ursa was sent flying back. Ruby immediately turned her head to see a yellow-haired girl with big blue eyes, hearts on the sides of her face, and was holding what appeared to be wand with half a star in the middle. Ruby was dumbfounded by the sight of this girl, and the girl appeared to be too. Not really knowing what to say Ruby said the only thing that came in her mind, "Hi there,"

"Hey," the girl said back, waving her free hand slowly in the air.

Before either girl could say a word, a might roar was heard. Both girls turned to see a herd of Ursa's rushing towards them. Ruby transformed the Crescent Rose into a gun and shot away, while the other girl used her wand.

The girl yelled, "Warnicorn Stampede!" as what seemed to be Unicorn's rushed towards the Ursa's taking some out but was mostly crushed by the Ursa's. As a Ursa drew near, Ruby transformed her weapon back into a scythe and sliced the Ursa in half. Two Ursa's appeared in front of Ruby out of no where and used their claws to cut her. Luckily Ruby managed to dodge these attacks and used her scythe to cut one's head off and stab the other the heart. Meanwhile, the other girl was having no trouble fending off the Ursa's. She was using her wand with Ruby thought was spells. The girl bewildered Ruby, if she was using spells than did that mean she was using magic?

If she was using magic then did that mean magic was real? Questions begin to circle in Ruby's mind as she tried to wrap her head around the girl. She appeared to be human, by the looks of her now she knew how to fight, and she appeared to be right around Ruby's age. A little bit younger actually. Before Ruby can think about her more she heard a Ursa rushing behind her.

(Star POV)

Star cast a spell on one of the monsters as another came after. Star was overwhelmed by how many monsters were here. The only reason Star thought she was alive was because of the red-and-black-haired girl fighting the monsters as well. Usually she had Marco to help fight off monsters, but she needed time away from him. After that stupid Love Sentence concert...

She had to hide her anger by fighting monsters, that's why she used her dimensional scissors to go to some random dimension she never been to before so she could get all the anger out. So she ended up in this dimension and it took her less than five minutes of wandering around to find monsters to fight. She immediately released all her hate on the monsters that were trying to kill her, but now she got all the hate out and is being a little bit overwhelmed right now. But she didn't want to bail on the other girl with a scythe. So she kept fighting. One of the monsters struck Star from the back sending Star crashing to the ground. As Star turned herself as the monster raised his claw to end Star, the girl with the scythe ran fast and beheaded the beast. As the girl came to lend Star a hand Star noticed some features of the girl:she had a red cloak which reminded Star of Marco's red hoodie, her attire was a black blouse and a skirt, and she had silver-eyes.

Star took the end the girl offered her and got up.

"Thank you," Star thanked the girl smiling.

"You're welcome," said the girl. "What are you doing out here in the Emerald Forest? Don't you know it's dangerous to be here without a team? My name's Ruby by the way."

"Star, and I'm just here to blow off some steam."

Just then, the monsters regrouped to form one last stand against the girls. Which at the sight of this Star and Ruby assumed battle stances. As the Ursa's rushed towards the two girls Star yelled, "Dagger Crystal Heart Attack!"

As heart shaped daggers took down a decent number of Ursa's Ruby used her Semblance took hack the rest of the Ursa's. While a large number of Grimm was taken out there were still four Ursa's left to kill the two girls. As the Ursa's ran towards the two girls from a long distance Ruby was about to finish them off but was stopped by Star grabbing her hand.

"Wait," Star said. "I have and idea."

Star whispered the plan to Ruby's ear and when she was done explaining the plan Ruby looked at her and smirked. Ruby backed away as the last of the Ursa's were approaching them at full speed but was hoping they would run fast as she yelled, "Supersonic Leech Bomb!"

The leech's landed just a few feet away from the Grimm as they exploded sending the Grimm into the air as Ruby used her speed to jump high enough and cut down the Ursa's in the air. As the last the Grimm disintegrated as the fell down Star ran up to Ruby and yelled, "That was awesome!"

"Yeah it was!" Ruby yelled back in the same excitement Star was in.

"I was all like 'blast blast' and you were all like "whoosh.'"

"With my speed and awesome weapon and your magic we're awesome together!"

"You need to meet my friend Marco!" Star said at the same time Ruby said, "You need to meet my team!"

(Time Skip)

(Star and Ruby POV)

After awhile of explaining things both girls were now coming to terms. Well, it was mostly Ruby sine this was her first time hearing of this "multiverse" of different dimensions, realities, and timelines ect. Ruby was also informed that Star was a princess from a world Mewni which reminded her of Weiss but Star was more like herself and Nora. She also now knows that Star was sent to a world called "Earth" to learn how to control her powers and befriended a boy named Marco Diaz who helps her learn about Earth. Star then explained that magic was real in some universes and 'not real in anothers.' Star ranted off on that for a little while. And she also explained some other stuff but Ruby really didn't most of it.

After Star explained herself Ruby then explained that she was in a world called the "Remnant" where monsters called "Grimm" want to kill all humans so there are schools where they train Hunters and Huntresses to kill Grimm. She also explained that there are a different species called "Faunus" where humans are mixed with animals and apparently there are hated for some humans for some reasons Star couldn't understand but what really Star was interested into was this "Great War" where all kingdoms of Remnant were at war with each other.

After all the explaining the sun was beginning to set which meant that Ruby had to leave.

"Oh, no." Ruby said. "Its starting to get dark. I should probably be getting back to Beacon before my team gets worried about me."

"You never told me about your team," Star said.

"That's right I forgot!" Ruby smacked her head. "I forgot to introduce you to my team! I know my sister would love to meet you."

Star looked at her phone and it seemed like it was getting late on Earth as well.

"Well I need to get back to Earth before Marco comes looking for me in the multiverse again." Star said.

"We need to meet again and with our friends!" Ruby stated.

"Agreed," Star said.

"The tournament is in a few weeks and my team will probably be wanting to train..."

"Now that you mention it graduation is coming up for me." Star said rubbing her chin. "But we need to meet again with our friends before all that stuff happens!"

"I know!" Ruby said worriedly. "What! What day is it for you today?"

"Monday," Star answered.

"It's Monday for me to. That's it! We're meet again on Saturday!" Ruby recommended.

"Perfect!" Star stated. "See ya!"

Star then used her dimensional scissors to go back home. Ruby watched it with amazement and said, "It'll get me awhile to get used to that."

(Ozpin POV)

Ozpin looked at the screen that was showing Miss. Rose talking to Star Butterfly. The daughter of Queen Moon.

"Oh, Moon," Ozpin moaned. "Who did you marry to have that offspring?"

To be continued...

Authors Note: Well I started writing this in May and it took me until July to finish it. This is a two-shot so I'll probably get start writing the second part sometime this week so I'm sorry this seems a bit rushed but I really want to get this done because part two is where all the character interactions and action REALLY starts! That and I'm starting to finish up some unfinished stories and I figured I get this finished before the Season 3 premiere of Star vs. begins. BTW, before I go I want you guys to know that the Ozpin knowing that Moon and Mewni exists is nothing more than a joke and to fill up the plot hole of all the cameras that Ozpin has laying around... what a minute... if he has all those cameras laying doesn't that means he can see...

This is Shadow The Jedi, ending transmission and as always, May The Force Be With You.