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When Ladybug arrived on the roof that night where she was due to meet Chat Noir for patrol, he hadn’t shown up yet. The only thing waiting for her on the roof was a giant cardboard box pushed up beside a chimney. And maybe it was a little hypocritical to be annoyed at him for being late when she was also late, but at least she’d had the decency to be less late.
Oh well, she thought, it’s not like I ever get enough sleep anyways. What’s a few minutes less? She settled in to wait for her partner, taking a seat and leaning back against the box for comfort.
But then she felt the box shake as the flaps opened behind her, and a voice shouted “Bugga-BOO!”
Ladybug screamed, jumping away and turning around—only to see her partner sitting there in the box, laughing hysterically. She glared at him, hoping her heart rate would soon return to normal.
“What the hell was that for?” she asked when his laughter had finally died down.
He grinned. “I’m Schrödinger’s Chat, ” he exclaimed excitedly, then burst out into giggles again.
Ladybug stared blankly. “What?”
“Get it? Because I’m a Chat in a box ?”
Sighing, she let her head fall into one of her hands, shaking her head slowly.
“I have literally no idea what you’re going on about Chat.”
Chat’s mouth dropped open. “How can you not know? It’s a thought experiment that a famous physicist came up with to explain the the phenomenon of superposition.” He tilted his head mischievously. “Or in this case, super-hero-position.”
“Again...What?”
The amusement finally faded from his face, replaced by a small frown. “Come on m’lady, don’t you have any appreciation for physics?”
Ladybug shrugged. “Sure I do. I appreciate that gravity exists—when it’s not making me fall to my death that is. And I’m a fan of indoor heating. I guess whatever makes cellphones work is pretty cool too.” She paused, considering. “Atomic bombs were admittedly not the best invention. But I’ll concede that usually, physics is pretty great. So long as I don’t have to talk about it.”
He didn’t seem impressed by her answer. “But it’s sooooo cool. Like have you ever heard about the uncertainty principle? Did you know that light acts like both a particle and a wave? Or do you know why—”
“Chat, we need to go on patrol.”
“But m’lady! I cannot in good conscious let you go around in the world without knowing about Schrödinger’s Chat.” He seemed genuinely horrified at the thought.
She groaned. “Fine, you can explain the box thing. But huuuurry. We need to patrol and I don’t want to be up all night.”
“Ok, ok, ok. So basically there’s a cat in a box, and a radioactive atom inside that’s hooked up to a device that can release a poison—”
“Wait, they’re poisoning the cat? Why do you seem so excited about this?”
“Well it’s a thought experience m’lady, it never actually happened. No Chats were harmed in the making of this science, I purrrromise.”
“But why does the fake cat have to fake die? ”
“Well it’s dead and alive. At the same time.” The top of his mask rose up and down as though he were wiggling his eyebrows underneath it, and his mouth hung open in a dorky sort of smile as if he was trying to convey exactly how cool this was. He paired the expression with a pair of finger guns pointed towards her, succeeding only in convincing her of what an absolute dork he was.
“That makes no sense.”
“It does if the box is closed.”
“If you don’t finish explaining this soon then I’m going to close this box again and see if you’re dead or alive.”
“Now that doesn’t make sense.” His eyes glinted in the moonlight, and Ladybug refused — she refused — to acknowledge how cute he apparently looked when he got all excited about science. “So,” he continued, “In whatever time the box is closed for, there’s a fifty percent chance that the radioactive atom will decay, and if it does, there’s a poisonous gas that will be released, which kills the cat. But—”
“You said it was alive and dead. But it really sounds like it’s only dead.”
“M’lady. You’re the one so insistent about finishing this so we can go on patrol. But if you keep interrupting me, we’ll be here all night.”
“Fine,” she grumbled. “Continue.”
“Ok, now where was I…?” His voice was way too smug. She was certain he was taking longer on purpose now.
“The. Cat. Got. Poisoned,” she said said through gritted teeth. Growing tired, she crawled back over to lean against the box. When he started speaking again, she could feel his breath warming the back of her neck.
“Hmmm. Right. Except you , the observer, the beautiful Ladybug waiting outside of the box—” she leaned her head back, looking up at him so he could see her roll her eyes. “—you m’lady don’t know if the cat is dead. Because there’s also a 50% chance that the radioactive atom didn’t decay, in which case the poison was never released, and the cat would still be alive. So you see, as far as you’re concerned, the cat is both dead and alive.”
Ladybug let the words sink in for a minute, considering. Then she shook her head. “No, it’s either dead or alive. It still can’t be both.”
“But you don’t know if it’s dead or a—”
“It’s alive. I choose for it to be alive. I’m just not putting the poison in. Or actually, I’m not even putting the cat in a closed box at all, because what if it suffocates . I won’t—”
Chat cut her off with very exaggerated sigh. He sounded almost as exasperated as she felt sometimes when his shameless flirting — in the middle of an akuma fight — got to be too much. “Fine, fine, fine. You don’t like the thought of a harmless kitty dying. I guess I can’t blame you...Ok, what it it’s me in the box?”
“HOW IS THINKING OF YOU BEING DEAD ANY BETTER?”
“NO! There’s no poison in this one. Just…Imagine I’m Chat Noir in a box, and I’m about to use my cataclysm—”
She turned back to face him and smirked. “If you use cataclysm on the box then I’m definitely going to know if you’re dead or alive.”
He fixed her with a glare. “Did I say I was using it on the box? I brought some other object in the box with me. So anyways, after I use cataclysm, obviously I’ll de-transform soon after. Except you don’t know if or when I’ve used it. So as far as you’re concerned, until the box is opened and you can see me, I’m both transformed and de-transformed.”
“No. You’re still either transformed or de-transformed. You can’t be both at the same time. Whether I know or not.”
“That’s not the point though—”
She shrugged. “I don’t know, I guess you didn’t explain it very well.”
“Ok well obviously a thought experiment about individual particles that uses a macroscopic example isn’t going to be a perfect analogy, but…”
They didn’t end up making it out on patrol that night. Instead she sat next to Chat, listening to him ramble on about various scientific theories and watching his face light up as he did so. As Marinette fell asleep later that night, she couldn’t help the small smile that slipped over her lips when she recalled his unbridled joy. Her akuma-fighting partner might be ridiculous, but she wouldn’t trade him for the world.
***
If Marinette had thought that the next day would involve significantly less talk about Chats and boxes, the minutes leading up to the start of class were about to prove her very very wrong.
“Hey Marinette!” said a chipper voice as Adrien walked into class, absolutely beaming. Instead of taking his seat in front of her he walked right up to her desk, leaning on the edge of it as he slipped his phone out of his pocket.
“A-Adrien, h-hi!”
“Look at this meme I found last night!” He waved his phone in front of her. She wasn’t sure she’d ever seen him look so excited.
It was an adorable expression on him. And even if Marinette had been desperately trying to get over her stupid crush on him recently, even if she was finding it to harder and harder to deny her feelings for a certain other boy with blonde hair and green eyes...Well...It was hardly her fault when Adrien looked at her like that and a part of her just melted.
So she smiled back, hoping her face was at least slightly less red than Ladybug’s suit, and looked at the meme. She wasn’t sure what she’d expected, since Adrien wasn’t normally the type to obsess over memes. She assumed he didn’t really have much time to peruse the internet aimlessly with all the things his father kept him busy with. But whatever she’d expected...it definitely hadn’t been this.
Because she was now looking at a badly photoshopped image of Chat Noir sitting in a box, with the caption on the top that read ‘Schrödinger’s Chat’.
And then she made the mistake of looking up at Adrien and she froze.
Because...Oh no. No way. That look in his eyes. She knew that look.
She’d know that look transformed or de-transformed. Dead or alive.
She must have taken too long to process, because she saw Adrien’s expression falter.
“Don’t tell me you don’t know about Schrödinger’s Cat either. It’s a thought experiment that explains—”
Marinette held up a hand to cut him off.
Because Holy Holy Holy shit, Adrien Agreste was Chat Noir.
She wanted to freaking scream right now, she was so happy it was him. But she had a reputation to uphold as Ladybug, so instead she simply lowered the phone and narrowed her eyes at Adrien.
“Kitty, I am so not listening to you explain that stupid box one more time.”
Because Chat might have been in the box, but he was definitely out of the bag.