It was a peaceful morning in the Land of Ooo. Finn and Jake were kicking back in their treehouse, debating their next adventure. Jake stretched lazily across the couch, his body expanding as he yawned. "Man, we haven't had a big adventure in days. I'm starting to feel rusty."

Finn, sitting on the windowsill, gazing out into the open landscape, scratched his chin. "Yeah, we need to find something exciting to do. Maybe we can visit the Fire Kingdom or see what Princess Bubblegum is working on."

Just as Finn was about to suggest another idea, a loud thud came from outside. Both he and Jake froze for a second.

"Uh… did you hear that?" Finn asked.

Jake nodded, now in a defensive stance. "Yeah, dude. Let's check it out."

They rushed to the door, Finn grabbing his sword on the way out, and swung it open. What they saw wasn't something they had expected. Lying at the base of their treehouse was a figure, draped in a dark cloak, his silver hair spilling out from under his hood. The guy looked unconscious, but his body had an odd glow to it—especially the strange tattoos that ran along his arms, which faintly shimmered in the sunlight.

The figure looked… human.

Finn's breath caught in his throat. "Jake... Jake, do you see this?!" he stammered, his voice filled with disbelief. "Is that… is that a human?"

Jake, stretching up to inspect the figure, frowned. "Whoa, dude. You're right. I think it is!"

Finn knelt beside the figure, his hands shaking slightly. "Another human? I've never met another human before… not since… not ever."

"Is he dead?"

Jake, squinting his eyes, stretched his body to nudge the guy. "Nope. He's breathing."

Finn crouched down beside the stranger and gently shook him. "Hey, buddy. You alright?"

Suddenly, the stranger's eyes shot open, revealing a piercing, glowing gaze. He blinked once, sitting up slowly, as if the impact that knocked him out meant nothing.

"Where am I?"

Finn, still wide-eyed and clearly shaken, barely managed to respond. "You're in the Land of Ooo… Who… who are you? Are you really human?"

The stranger's gaze softened as he looked at Finn, sensing his shock. "Yes, I'm human. My name is Xander."

Finn blinked, trying to process everything. "Xander… you're a human…" His voice trailed off as the realization truly hit him. "I've never met another human before… You're the first."

Jake, ever the practical one, floated down beside Finn. "Yeah, it's kinda crazy seeing another human around here. What's your deal, man? You crash-land in front of our treehouse for fun?"

The stranger blinked again and shook his head slightly. "I didn't crashed… not exactly." He stood up, surprisingly steady for someone who had just been unconscious. He was taller than Finn, with a strong, battle-worn presence. "I'm Xander."

Jake floated up beside Finn, arms crossed. "Okay, Xander. So why'd you drop by out of nowhere?"

Xander sighed, his face hardening slightly as he tried to remember. "I've been traveling for a long time. It's hard to explain, but I've been searching for something… or someone." He looked around, taking in the treehouse and the vast landscape. "This place… Ooo… it's different from where I've been."

Finn, his curiosity piqued, sheathed his sword and extended a hand to Xander. "Well, I'm Finn, and this is Jake. If you need help finding whatever you're looking for, we can lend a hand. That's what we do."

Jake, stretching into a more laid-back form, added, "Yeah, man. We're all about quests and stuff."

Xander shook Finn's hand, a slight smile appearing on his otherwise stoic face. "Thank you. I could use some help."

Later that day, after getting Xander settled into the treehouse, Finn and Jake decided to take him on one of their usual rounds through Ooo. First stop: the Candy Kingdom.

"We gotta introduce you to Princess Bubblegum," Finn explained as they trekked across the open fields. "She's super smart and usually knows a lot about weird stuff. Maybe she can help you figure out what's going on."

Jake nodded, floating lazily beside them. "Plus, the Candy Kingdom is a cool place to hang out."

As they approached the bright and colorful kingdom, Xander's eyes widened slightly. "I've never seen a place like this before."

"You'll get used to it," Finn said with a laugh. "It's a pretty sweet gig."

When they arrived at the castle gates, Princess Bubblegum was already waiting for them, her usual lab coat on, clipboard in hand, and a smile on her face. "Finn! Jake! What's up? You guys here to help with my latest experiment?"

"Not exactly," Finn replied, stepping aside to introduce Xander. "This is Xander. We found him outside our treehouse this morning. He's looking for something, but we're not sure what. Thought maybe you could help."

Princess Bubblegum eyed Xander curiously. "Interesting. Those markings on your arms… they're not like any magic I've seen before." She offered a friendly nod. "I'm Princess Bubblegum, ruler of the Candy Kingdom."

Xander, always composed, gave a slight bow. "It's an honor to meet you, Princess. I come from a place far from here, and I'm trying to understand where I am."

Bubblegum's interest piqued. "You're not from Ooo? Hmm, this could be fascinating. I'd love to run some tests and see what kind of energy flows through your tattoos. It might give us a clue about where you came from."

Finn, now looking excited, grinned. "See? PB's got all the brains!"

Xander glanced down at his arms, where the faint glow of his tattoos pulsed slightly. "If you think it'll help, I'm willing to try."

Before they could dive into any experiments, an alarm rang out across the kingdom. "Oh no," Bubblegum muttered, her expression darkening. "We've got a situation."

"What is it?" Finn asked, immediately on guard.

"One of the ancient lava beasts from the Fire Kingdom is rampaging toward the walls," she explained. "I need to stop it before it destroys everything."

Xander's eyes flickered with interest. "A lava beast?"

Finn unsheathed his sword, eager for action. "Sounds like the perfect time for you to see what we do best, Xander!"

Jake stretched himself into a giant shield. "Yeah, man! Let's go wreck that lava monster!"

The trio, led by Princess Bubblegum, rushed toward the outer walls of the Candy Kingdom, where the enormous lava beast was already wreaking havoc. The creature was made entirely of molten rock, its glowing red eyes blazing with anger as it stomped toward the castle.

Finn and Jake charged forward, ready to fight, but Xander calmly stepped forward, holding out his hand. His tattoos glowed brightly as he summoned a massive blade made of pure energy. "I've got this."

With one swift motion, Xander leaped into the air, his sword slicing through the beast's molten form like butter. Lava splashed around them, but his movements were fluid, almost graceful, as he struck at the creature's core.

"Whoa!" Finn said, watching in awe. "Xander's a beast!"

The lava monster roared in pain, but Xander didn't hesitate. With a final, powerful strike, the beast crumbled to the ground, defeated.

As the dust settled, Princess Bubblegum approached, her eyes wide with amazement. "That… was incredible."

Xander's sword vanished, and his tattoos dimmed once again. He looked at Finn and Jake, who were grinning from ear to ear.

"Welcome to the team, Xander!" Finn cheered, giving him a thumbs-up.

Xander nodded, his smile barely visible but sincere. "Glad to be here."

And so, the adventures of Finn, Jake, and their new mysterious friend, Xander, had only just begun. Little did they know, this was the start of something much bigger.