I've seen a lot of Mario & Sonic crossover stories where the two heroes team up together. These stories are actually my favorite kind of crossover stories! I have a lot of favored stories of this kind on my profile, but only the complete ones however, because a lot of these stories are still unfinished.

After reading a lot of stories like that, I thought: why not I write one as well? And that's exactly what I'm going to do!

Alright, In my case, this story takes place after the events of Sonic Colors and during the events of Super Mario Galaxy, since this game is one of my all time favorite Mario games.

So, I really hope you enjoy this story. And please don't forget to leave a review! That would make me even happier and more motivated to continue this story!

Without further ado, enjoy! ;)

Chapter 1: Prologue (Part 1)

In a place called Mobius, there lived a blue sapphire hedgehog with emerald eyes, pure white gloves and shiny red sneakers with white stripes and gold buckles. He's a supersonic hero who saves his homeland from the clutches of an evil scientist who plans to build his own empire by capturing animals and turning them into robots.

This hedgehog's latest adventure took someplace much further than Mobius itself; it was an adventure in outer space! This time, the evil scientist builds a big interstellar amusement park in space to distract the customers while he captures the mysterious aliens known as Wisps to use their energy for a Mind-Control weapon. But, fortunately, our blue blur hero put this plan to a stop, saving the aliens and breaking the chains used to drag these Wisps' homes into the 'amusement park'. He received the help of his trusty two-tailed yellow fox friend to translate the Wisps' language.

By foiling the scientist's plan, the hedgehog made back to his home safely with the Wisps' help. He and his fox friend bid the aliens a fond farewell.

The two friends were now making their way back to their friends while also having a conversation.

"Heh, who knew that egghead, would build an amusement park in space just for distraction? If it weren't for you, buddy, we would never be able to track his evil plot!" the blue hedgehog known as Sonic said, clenching his fists.

"Yeah, that man is a sore loser. But still…" the fox known as Tails sighs deeply. Sonic noticed his adoptive bro's sudden sadness and became worried.

"What's wrong, Tails?" Sonic asked in concern.

"Huh? Oh, it's nothing. It's just that I miss Yacker." Tails answered.

"Oh, I know how you feel, bro." Sonic said in a soft tone.

"Really?" Tails was astonished.

"Of course! I know you got a little depressed because your translation thingy worked just when it was time for saying goodbyes, but I know, buddy, that deep in your heart, Yacker still remember us." Sonic responded, placing his index finger at Tails' chest. Tails smiles softly.

"Thanks, Sonic. You're really a good friend." He replied in a soft voice.

"No problem!" Sonic gave thumbs up and winked. They both chuckled and continue their walking.

Unknown to them, a mysterious person from the cosmos was watching them trough a vortex portal.

"So this is Sonic, the blue hedgehog who saved the Wisps in outer space…" she spoke in an interested tone. As she speaks, her voice echoes, which was weird. "I must say I'm quite impressed at his actions. Let's see what's happening at my dimension now…" as she opens another vortex portal.

Meanwhile…

"GRRRRR! I HATE that pesky hedgehog!" the evil scientist named Dr. Ivo Robotnik who goes by the name Eggman growled, because his plan was foiled. He was riding in his Eggmobile.

"You seem angered right now, sir." A red round-headed robot named Orbot said.

"Angered?! I'm more than that! I'm MAD!" Eggman shouted at Orbot's face.

"Can you stay calm, sir? Just for a little bit…?" the yellow cubic-headed robot named Cubot asked stupidly. Eggman glared at Cubot.

"Silence!" Eggman slapped Orbot and Cubot, making them spin around and fall backwards.

"I must think of something brilliant if I want to stop that menacing hedgehog. Like, I have the brains but where is the strength?" Eggman asked himself, placing his hand on his chin.

"Oh, I know! Make a stronger robot!" Cubot said, standing up.

"That's what I usually DO!" Eggman shouted at Cubot's face. "I'm not talking about robots! I'm talking about an actual person! I need someone strong, fierce, and just as intelligent like me."

All of a sudden, a black vortex appeared out of nowhere, right in front of the Eggmobile. Eggman, Orbot and Cubot were startled by that.

"AAHH! Mayday! Mayday! We better get out of here!" Cubot screamed horrified. As Eggman turns on the engine, he suddenly started to get sucked by the black vortex.

"Gaaahhh! I'm getting sucked by it! Help me, morons!" he shouted while holding on to his Eggmobile with one hand.

"Yes, sir! Operation Knowledge, activate!" Cubot said.

"No, you idiot! I said help me out of this!" Eggman shouted in anger. He was starting to lose his grip.

"So, what do you want to know, sir?" Cubot asked. But, Eggman loses his grip, and was pulled into the vortex.

"Aaaaaaahhhh!" he screamed as he gets sucked. As soon as he entered the vortex, it disappears.

"Umm, did I miss something?" Cubot asked confused. Orbot shook his head and face palmed.

In a different dimension, there was a land filled with mushrooms, pipes, and all sorts of mushroom-like creatures. This place was the Mushroom World. At its center was a castle where this place's monarch lives and rules over it. However, at the other side of this world was a deserted lava-filled world, with a castle as well. Its ruler was a big bad turtle guy who can breathe fire like a dragon. His goal was to rule the entire Mushroom World by kidnapping its princess and force her in marriage. Thankfully, this world also has a hero; a Italian plumber with brown hair, a long round nose, blue eyes and a mustache, wearing a red cap with an 'M' on it, red shirt, blue overalls with yellow buttons, all-around white gloves and sturdy brown shoes. He always ends up defeating the Koopa King over and over, and rescuing the princess. We could say that this plumber became the Mushroom World's protector.

Right now, the Koopa King, whose name is Bowser, was with a koopa wizard named Kamek, who was the one who took care of Bowser since he was a kid.

Kamek had casted a spell with his wand to create something useful for the Koopa King's new plan. But the spell, instead of creating something, ends up becoming a portal.

"You call THAT a useful thing?! Are your spells berserk again?!" Bowser roared at Kamek.

"I-I'm sorry, your majesty! Damn, why are my wands turning berserk that quickly?" Kamek grumbled.

"Well, you better work on your spells more precisely." Bowser said sternly.

"Hmm? Sire, look! Something is coming from the portal!" Kamek pointed at the portal. Eventually, an egg-shaped man came out from it. The portal disappears.

"Ow… What just-?" the man groaned as he stood up. He opens his eyes only to notice unfamiliar surroundings. In front of him were a big and a short turtles.

"Whoa! Who are you? Where am I?" the man panicked.

"Now, now, stranger. Do not panic." Kamek said, trying to calm the man down.

"You're right now inside my Castle. I'm Bowser, the almighty Koopa King. And this is just Kamek." Bowser said, introducing himself and Kamek. "And you are?"

The man then cleans his throat.

"I am Dr. Ivo Robotnik, but I'm most known as Eggman for some reason." The man who was Eggman introduced himself.

"That makes sense, since your body is shaped like an egg." Kamek pointed out. Upon hearing this, Eggman glared at Kamek.

"Oh, my bad." Kamek responded, scratching his head, embarrassed.

"Anyways, I've never saw a castle or anything like that in Mobius!" Eggman said impressed by the castle's structure. Bowser and Kamek were confused.

"Mobius?" Bowser asked.

"Is that place where you came from?" Kamek guessed.

"Yes, it is!" Eggman exclaimed. "Wait… I'm not in Mobius?"

"No, you are in the Mushroom World." Bowser said.

A moment of silence was triggered.

"Interesting, quite interesting. That portal I've just created might be an interdimensional portal, I presume." Kamek concluded. Bowser just ignored Kamek's conclusion, and asked Eggman:

"Say, what exactly happened to you before you came here? Did something happened in your… Dimension or something?"

"Well, before I was sent here, I remember that I was heading back to my lair after having my plan foiled again, until this black vortex came in and sucked me into here." Eggman answered.

"Hold on, did you just say… 'Lair'? And 'plan foiled'?" Bowser asked.

"Why yes, it's so annoying! You see, my goal was to build my own empire, but my plans are always foiled by that pesky hedgehog Sonic!" Eggman growled, punching a wall.

"I see… I can feel your pain too." Bowser said.

"What do you mean?" Eggman asked.

"You know, my goal is to take over this world by forcing Princess Peach, the ruler of the Mushroom Kingdom into marriage, so I always plan something to capture her. But that stupid plumber Mario always foils my plans! And he rescues Peach, taking her back to her Castle! That makes me so FURIOUS!" Bowser shouted in anger, and stomped the floor, causing a small earthquake.

"Well, well, looks like we both share something in common, Bowser." Eggman snickered.

"Hmm, you might have a point there, Eggman." Bowser pointed out.

"So, are you planning something else to capture the Princess?" Eggman asked. "I would've plan something genius if I was replacing you!"

"I am. I'm planning to take her Castle into outer space and build my own empire at the center of the universe." Bowser answered.

"Oh, I've already built an empire in outer space already! I called it the Death Egg!" Eggman smirked.

"If that's the case, since you're an evil genius or something, could you help me build something in order to take Peach's Castle into space?" Bowser asked.

"Sure! It's a deal!" Eggman responded.

"Okay then, for now on, we'll join forces together." Bowser said, offering his hand to Eggman.

"With my pleasure." Eggman said and shook Bowser's hand.

It seems that an evil alliance is happening now…

To be continued…

So, there's the first chapter! I promise that I'll continue. Please review!