Yay, more crossover time!

I own nothing you recognize as canon. I also do not own any of ArtemisApollo97's OCs.

Two: Differences

"Okay, I don't get it," Espie said while scratching her head. "Percy has a twin sister? That sounds so unreal."

Charlie shrugged. "It's normal for me. What sounds unreal is Dad actually marrying that Titan lady. Isn't she, like, a thousand years older than him?"

"Three thousand," Espie corrected. "And Papi loves Mom. Even Piper said their love couldn't be stronger. They're literally tied together by their Fate-strings! I can't see him being with anyone else."

"Not saying it's a bad thing or a lie!" Charlie held his hands up in surrender. "It just sounds…wrong to me. When I think of Calypso, I think she's lounging on a beach somewhere with boyfriend three hundred-something without a care in the world."

Espie shivered. "I'm getting freaked out by this."

"Me too."

They arrived at Charlie's place, which looked like a normal house in a cul-de-sac with a garage attached. The garage door was open, revealing a complicated machine shop. A bronze van was parked on the street.

"You have a car?" Espie asked. Her family had no use for a car, since everything in New Athens was walking distance, as was camp. If they traveled outside the borders, pegasi and Festus usually worked as transportation.

"How else do you think we get around?" Charlie retorted.

"Festus!" Zac screeched, plowing ahead into the shop. A bronze dragon head lifted up from the back of the shop, its ruby eyes glowing curiously.

Zac ran up and hugged the automaton happily. "Hi, Festus!"

The dragon reared its head in alarm and spewed oil. Zac ignored the oil and hugged harder.

Charlie tilted his head. "Weird that he knows Festus, but Festus doesn't know him."

Espie shrugged. "I don't know how this is, either."

Zac looked around, confused. "Where are the TFs?"

"TF?" Charlie asked.

"Tiny Festus," Espie explained. "They're literally mini Festus robots. Papi made them as an outer defense system—only, TF Mark 1 decided it wanted to be independent and was reassigned as the babysitter when Tulio and I were born. He was also kinda the tattler when my brother and I got into mischief."

Charlie snickered. "Interesting…Dad never made things like that. I bet he'd wish he had when I was born."

Espie's eyes lit up. "You were a troublemaker, too?"

"Of course! You can't look like Dad and not be annoying!"

They high-fived.

The door connecting the garage and the house opened. Out strode Leo Valdez, eating an apple. He froze mid-bite when he saw Zac. His whole expression just screamed, Huh?

Espie narrowed her eyes. This wasn't her Papi. This guy was clean-shaven, older—maybe lower to mid-forties?—and way skinnier. Her Papi was much more muscular and broader than this guy. Trouble was, this Leo, sans the earlier differences, looked exactly like her Leo; same old tool belt, same fashion sense, same grease-stains, same oil-slicked, curly hair—he was the same!

Leo's eyes traveled to Espie and Charlie. They widened upon seeing Espie.

"So," Charlie drawled. "Instead of getting jam, like I said I would, I found something interesting. Dad, meet my sister, Esperanza."

Leo spat out the apple pieces in his mouth. "Excuse me?" he yelped. "Run that by me again, please!"

Espie held Charlie's shoulder firmly. "This isn't my Papi. Mine is younger than this, and not as skinny."

Leo just blinked at them. "Am I having a mid-life crisis, here? What the Hades is going on?"

Zac rocketed toward him. "Papi," he shouted. "I gave Espie the dolphin! She said she loved it!"

Leo didn't reciprocate the hug the child was giving him. "What dolphin? Who are you? WHAT IS HAPPENING?"

Zac pulled away and tilted his head at the son of Hephaestus. Then, he grimaced. "You aren't Papi. Papi is nice! You mean!"

Leo's jaw dropped. "What?"

Espie walked closer. "I think there may be a misunderstanding here." She stuck her hand out. "Hi, I'm Esperanza Grace Valdez, daughter of Calypso."

Leo staggered backwards. He shook his head. "No," he mumbled as he clutched his head, as if in pain. "No, no, no, no, no! This isn't happening! I never did that with Calypso! We never—!"

Espie steadied him. "Um, I don't think it was with you. My father is Leo Valdez, son of Hephaestus, but—"

Leo snapped his head toward her. "No, I'm not! Calypso must have—"

Espie growled at him, her fiery aura rising up. "Listen, will you? Geeze, you're worse than my Papi!"

Leo took a step back, realizing it was her fire user nature that had appeared in front of him. He looked at Charlie, who shrugged and said, "I know. Freaky, right?"

Espie put her hand to her chin. "My father doesn't live in New York City, he lives in New Athens."

"Excuse me—where?"

"Shush. He's also not as old as you."

"Wow."

"And not as skinny."

"Can you not—?"

"And I definitely don't have three new siblings that happen to be children of Percy Jackson's sister—whom I didn't even know about until today."

Leo cocked an eyebrow at that. "You didn't? I think Calypso met Lou a few times…"

Espie shook her head. "No, that's not it. Let me explain: Zac and I were in the Big House back at camp when this mirror transported us into an alley. 'Couple minutes later, we run into Charlie."

Leo scratched his chin. "A mirror that transported you here?"

"Yeah. I think…" she thought for a moment. "I think this is a different reality. The mirror said something about reflections…Maybe this world and my world are reflections of each other!"

"You've lost me," Charlie said.

Leo shook his head. "You've hurt my head."

Espie shrugged. "I'm hurting my own head, but I think that's what happened."

"If I'm really you're father," Leo drawled. "Then…um…hang on, lemme think of a smart question to ask that only my children would know."

Espie rolled her eyes. "You're a son of Hephaestus, the only child of Esperanza Valdez (Sr.), the head builder of the Argo II, savior of Olympus who decided to kamikaze Gaea. You make awesome tofu tacos and burgers, love pranking with Mr. Jackson and the Stolls…"

Leo blinked. "Okay, then…Maybe you Googled me. What's my favorite color?"

"Red."

"Who do I consider my sister, but she isn't my real sister?"

"Piper McLean, though I suppose she's Piper Grace to you, too?"

Leo nodded. "Who among the Seven do I fear the most?"

"Annabeth Jackson, cause she has no powers and almost stabbed you the first time you met."

Leo nodded again. "Checks out. But…this is awkward, meeting a daughter I didn't even know I had…"

Espie giggled. "Don't worry. I'm a twin. And, except for Zac, there's one more daughter after Tulio and I that you haven't seen, either."

"Wait, so which one is this? Zac or Tulio?"

Espie rolled her eyes. "I'm first-born, with my twin Tulio. Aria comes next, and finally is Zachariah."

Zac pouted. "Don't say that."

"Right, he prefers Zac, just like I prefer Espie over Esperanza."

Leo pinched his eyebrows together. "Oh, gods, this is a lot of kids I've apparently had with Calypso…all of you are Calypso's right?"

"Yes," Espie said.

Suddenly, a bronze-tipped arrow was impaled in the wall, inches away from Leo's ear. A few black curls floated down to the ground. Leo broke out into a sweat, his eyes wide as saucers. Espie, Zac, and Charlie turned around to see an angry woman with long black hair and stormy green eyes snarling at the group. She had another arrow notched on her bow, aimed at Leo's heart.

"Ya wanna run that by me again, Leo?" the woman growled. "Who had children with Calypso?"

Leo gave a nervous smile. "I…I can explain, sweetheart…" He tried not to squeak out the next words: "I love you?"

A/N: Decided to let it just be Artemis's world this time around. Next chapter will be my universe, to check up on my Leo and Tulio.

And trust me, Lou is violent by nature, and I'm sure she would be very mad at anyone insinuating Leo cheating on her D: