This is being cross-posted from Ao3. It was originally posted on 31 October 2019.

Huge thank you to GaeilgeRua for letting me use her Grammarly. Any other mistakes are definitely my own... I'll fix them eventually.

Disclaimer: Harry Potter belongs to JK Rowling, Bloomsbury, and Warner Bros. Marvel belongs to Disney. No copyright infringement is intended.

Prompt: Person A meets Person B on Halloween, and both think the other is dressed up in their Halloween costumes - Wizard and Superhero. Hilarity ensues, MMFBingo19 Square O3: Uniform Fetish, #ExcelsiorBingo19 Square: O5 Halloween

"I promise to try and make the party," Ginny told Hermione over the phone. She looked around the cluttered changing room, eager to get Quidditch practice over with so she could enjoy some Halloween festivities. "As soon as practice is over, I'll floo to your flat."

"Okay," Hermione replied, her voice slightly elevated due to the music in the background. "Try and get here as soon as you can. So many people have already arrived."

"Will do," Ginny said as her captain called for her from the doorway. "I've got to run. See you later."

"Bye," Hermione said, and then Ginny hung up the phone.

At this rate, she was going to have to go to the party in her Quidditch uniform. With a heavy sigh, Ginny followed the rest of her teammates out onto the pitch. She would do her best to try and get out of there early.

Steve couldn't believe he was stuck patrolling the streets of London on Halloween. Why couldn't Tony have asked Peter to take care of things? Oh right… The kid had a school dance he needed to attend. Sighing, as he put on his mask, Steve couldn't really blame him. Peter was still a teenager and deserved a few nights off now and then to have fun with his girlfriend and friends.

Besides, his shift only lasted a few hours, and then he could join up with Tony and the rest of their Avenger friends for some drinks and Halloween festivities. Apparently, he was supposed to meet them at 12 Grimmauld Place for a Halloween party thrown by Tony's on-again, off-again girlfriend, Hermione. Steve knew little to nothing about Hermione and her group of friends, so this would be an opportunity for everyone to meet.

Luckily, despite a few mischievous kids lurking about, the streets were safe, and Steve was able to finish his patrol without any issue. With a quick check of his watch, he did determine there was no time to stop back at his hotel and change, so he had to go directly to the party. It took him some time to find the right street, but he swore he missed the house several times as he walked back and forth.

Seemingly out of nowhere, a redheaded woman dressed in strange attire appeared next to him. After noticing she held a broom, he surmised her to be in costume as a witch, though he knew not what kind. Her cheeks were flushed as if she'd been exerting herself. Maybe she had run here? Steve thought he was lost, so he figured to ask for her help. "Excuse me," he asked, "Do you happen to know where 12 Grimmauld Place is?"

"Sure do," the witch replied with a smile. "I'm actually headed there myself." Pointing at the block of townhomes, she pointed to a door that Steve swore hadn't been there before. "Twelve is a bit difficult to spot if you don't know exactly where to look." She winked at him as if he was missing some sort of joke.

"Thank you," Steve replied with a nod of his head. "I would have been walking back and forth all night. I swear I never even saw the door."

"It's no problem," the witch said and then gestured. "Come on, then, let's head inside. I'm Ginny, by the way."

"I'm Steve," he told her before following her up the few stairs that led to the simple porch.

"Nice costume, Steve," the redhead said to him as they reached the door, and she used the knocker to get the attention of the guests inside. "I didn't have time to change into mine."

"This isn't my- Wait, you're not in costume?" Steve inquired, glancing at her up and down briefly before his cheeks flushed and he had to glance away. Coughing to clear the embarrassment from the air, he said, "I thought you were a witch."

"What?" Ginny asked in confusion as she looked Steve up and down. "You don't know…"

Before Ginny could finish her sentence, the door burst open to reveal a rather drunk Hermione and Tony clinging to one another dressed as pirates. Tony reached forward and grabbed hold of Steve. "Capsicle, you made it! Come and have a drink with me."

In the next instant, Ginny was left alone with Hermione. "So that was actually Captain America and not some guy named Steve dressed up in a ridiculous Star-Spangled outfit?"

"What?" Hermione said and then dissolved into laughter. "Of course, it was! I thought you knew this was a mixed party?"

Ginny shrugged as she stepped into the house and shut the door. "I don't think he got the memo about the costumes. Then again…" She trailed off as she glanced down at her Quidditch robes. It was no wonder Steve thought she was a witch. "Hermione? Does Tony and the others know that you're a witch?"

Hermione shrugged and then led Ginny toward the kitchen where the table was laden with food and drinks. "Tony knows, but I don't think he's told anyone else yet. After tonight, I assume they'll all know."

"Good to know," Ginny replied as she eyed Tony talking to Steve in the room across the hall. "I'm going to go and change into my costume. I'll catch up with you later, 'Mione."

A little while later, Ginny found Steve standing in front of the Black Family tapestry. His face was scrunched up in curiosity as he watches the depictions of the ancient family move as if by, well, magic. He'd changed out of his Captain America uniform and donned something a little more traditional for Halloween.

"I see you've swapped out your uniform for something out of Great Gatsby. Too bad, I like a man in uniform," Ginny said as she sidled up to the Avenger. Apparently, she would have to have a conversation with Hermione about these matching costumes, but for now, she wanted to get to know Steve a little better. "Having fun?"

Steve picked at his costume uncomfortably. "This wouldn't be my first choice in costume, but it's all Tony had extra." Glancing around the somewhat occupied room, Steve seemed to examine the people he was meeting for the first time. "I'm having a nice time. It's just that everyone seems a bit…"

"Magical?" Ginny supplied with a smirk. Feeling a bit playful. Ginny did a little spin, so the stands of her black flapper dress billowed out and back in again.

"I suppose you could put it that way," Steve said, unable to hold back a smile at her flirtatious behaviour. "I'd love to hear more about your change in costume."

"How about we grab some drinks and I fill you in on my little secret?" Ginny said, placing a hand gently on Steve's forearm.

Steve looped their arms together and began leading the way back toward the kitchen. "Sounds like a great idea to me," he told Ginny with a smile. "And, just so you know, I can always change back into my uniform later if you want to take a close look."

Ginny almost blushed at his comment but laughed heartily instead. This was going to be one exciting Halloween, of that Ginny was certain. After a few drinks and revealing that she really was a witch, who knew where the night would lead? Ginny could only hope that it went in the right direction.