A/N: This crossover is so overused, but as it's my first, to heck with being original.

Disclaimer: Don't own Heroes of Olympus, PJO, Harry Potter, or the Avengers. Still, * sighs * wishful thinking…

Chapter One

Percy P.O.V., Camp Half-Blood

Just when I thought I could get a break, my city was destroyed.

I mean, really? Leo had just gotten back from his re-birth to find Calypso, Reyna and Nico were staying in Camp Half-Blood for the year, and my Wise Girl was beautiful as always. I was thinking about taking her to Europe, sans monsters/Gaea, where we could relax. Everything was perfect.

Of course, two weeks after normality (or as close as we could get), Chiron called us to the Big House for a sort-of quest. His attempt to calm us down was drowned by shouts of rage.

"What?!"

"No. Absolutely not again."

"It's been two weeks!"

"It's Manhattan," I sighed. "I gotta go, for Mom and Paul. It's Kronos over again, but at least I'm defending my home."

"Well, whatever you do, we do with you," exclaimed Piper. I was a little suspicious, because it sounded like she had wormed a little charmspeak into her exclamation.

"Yeah, Seaweed Brain," Annabeth teased. "You are never doing a quest without me." I love Wise Girl. She's always been there for me.

"So," Leo jumped up, rubbing his hands together. "All we gotta do is take out those robot-alien-monsters. What are they called again?"

"Chitauri," groaned Jason, nudging Leo in frustration. "Honestly, were you listening?" "Ah- would you be angry if I said no?" "Gods, Leo. Oh yeah, we also need to get that guy Loki, or whatever. What's up with this whole, 'Norse gods are real too' thing anyway?"

"I know, too much for my poor little ADHD demigod mind to handle," I complained, and was promptly told to shut up by Frank and Hazel.

Harry P.O.V., 12 Grimmauld Place

You'd think defeating Voldemort would be enough.

I was finally ready to accept the deaths of those I loved, and wave good-bye to Ginny. Ron and Hermione were working together on a new teaching career, and Teddy Lupin seemed delighted to have a godfather. I wondered if that was how I would've lived, if Sirius hadn't been blamed, if I hadn't had to live with the Dursleys.

Headmistress McGonagall called me (along with Ron and Hermione, of course) up to her office, to discuss an invasion. One tiny problem? It was an alien invasion, in America. None of us had ever visited America, or even known about aliens! What did we owe them, anyway? Some of their lot could save the bleedin' world for once.

"Nevertheless," McGonagall sighed, "We have an obligation to the Americans, for the leader is a magic-user, though not of the wizarding heritage." Silence reigned for several seconds, before we agreed wearily. It had only been two weeks, after all.

Clutching the portkey (a toothbrush) tightly, I was filled with nostalgia for the Quidditch World Cup. In fact, that was the last thought roaming through my head as we vanished.