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The first hour after the time travel jump was fine. Uneventful. Almost boring. Marty would talk, Casey would listen. But then things started slipping sideways in ways that were… embarrassingly specific.
“You’re doing that thing again,” Marty said, glancing over at him.
Casey snapped his eyes away. “What thing?”
“Staring,” Marty replied. “Like you’re trying to solve a math problem on my face.”
“I’m not,” Casey muttered, cheeks warming.
Marty smirked. “Uh-huh.”
They walked in silence for a moment. Casey focusing on the sound of their footsteps, the rhythm of it, hoping it would ground himself. He felt sick, but not nauseous, it was really weird. He just didn't feel like himself. He was not going to spiral. It was just fatigue. Or nerves. Or-
“You smell like engine oil and static.”
The words escaped his mouth before his brain caught up.
Marty stopped in his tracks.
Casey stopped breathing.
“…Excuse me?” Marty said slowly, his tone sounding confused and even a bit surprised.
Casey’s hands clenched at his sides. His heart pounding. “I-I didn’t-”
“You just said I smell like engine oil and static.”
Casey squeezed his eyes shut. “I think I’m dying.”
Marty barked out a laugh. “What?”
“I didn’t mean to say that,” Casey said miserably. “I was just thinking it.”
Marty’s grin grew wider. “You think about how I smell?”
“No! I mean- not like-” Casey wouldn't stop stuttering, his words almost always coming out wrong. Casey waved his hands uselessly, face blazing. “Please stop talking.” Casey muttered, his cheeks burning from embarrassment.
Marty laughed, genuinely amused. “Man, Doc is gonna lose his mind over this.”
Casey groaned. Pinching the bridge of his nose. “This isn’t funny.”
“Oh, it is,” Marty said. “I mean it’s a little funny.”
Casey risked a glance at him and immediately regretted it. Marty was smiling like he’d just discovered a new toy.
“You’re enjoying this,” Casey accused, making sure his steps forward were just a bit quicker.
“Maybe a little,” Marty admitted. “You’re kinda adorable when you’re flustered.”
Casey made a strangled sound. “Please don’t say that when I’m like this.”
Marty paused. “Why?”
Because if he did, Casey was pretty sure something worse would slip out.
----
By the time they got back to the garage, Casey was a wreck.
He stuck close to the workbench, arms folded, eyes glued to the floor like it might swallow him whole. Marty, meanwhile, hovered near, curious, amused, and clearly waiting for the next slip.
Doc barely looked up from his notes. “Any unusual sensations?”
“Yes,” Casey said instantly. “Everything.”
Doc blinked. “Care to elaborate?”
Before Casey could stop himself-
“Marty’s heartbeat is loud when he’s near me.”
The garage went silent.
Doc slowly lowered his clipboard whilst Marty stopped breathing. Casey felt his own soul leave his body.
“I-” Casey clapped a hand over his mouth. “I didn’t- I swear I-” Casey stammered, tripping over his own words, desperate to get a explanation out.
Marty stared at him, eyes wide, then glanced over at Doc. “Is that… normal?”
Doc adjusted his lab like coat, fascination written all over his face. “Fascinating. It appears the temporal interference has weakened certain cognitive filters.”
Marty turned back to Casey. “…So you’re just saying whatever you think?” Marty continued to question. Casey nodded miserably.
Marty’s expression softened, amusement giving way to something quieter.
“That must suck,” he said, his tone shifting to something genuine. Casey let out a shaky laugh. “You have no idea.”
Doc cleared his throat. “It should pass within twenty-four hours. Possibly sooner.” Casey exhaled in relief, letting out the breath he didn't know he was holding. Marty frowned. “Possibly?”
Doc smiled. “Time travel is unpredictable.” That was not comforting.
---
The first sign that it wasn’t just Casey anymore came roughly three hours later.
They were sitting on the hood of the DeLorean, sharing a bag of chips Marty had somehow found, when Marty frowned mid-chew.
“Do you think I talk too much?” Casey blinked.“What?” he responded. Marty froze.
“…Why did I say that out loud?” Casey’s head snapped up. “Marty..”
Marty swallowed. “I was just thinking it.." Casey stared. “Oh no,” he whispered.
Marty laughed nervously. “Okay, that’s weird." Casey scooted a little closer without thinking. “How long has it been happening?”
Marty rubbed the back of his neck sheepishly.“Uh… since you smiled at me just now.”
Casey’s cheeks heated. “I smiled?”
“You do this thing,” Marty said, eyes refusing to meet Caseys. “Like you’re trying not to, but it happens anyway.”
The thought of Marty noticing such small details about Casey made his heart race.
the sun had started to set, the sky shifting to colors of orange, pink, and purple. The last light of the sun casted onto Marty, bringing out his features more.
"You look so good right now." Casey said. As soon as the words left his mouth, his slapped a hand to cover it, obviously too late. Marty's eyes widened, turning to look over at Casey. If you look really closely, you would be able to see a hint of pink starting to spread across his cheeks. "Oh wow." Marty said, chuckling nervously.
"Wait! I- ugh! Okay okay,” Casey said quickly. “New rule. No thinking.” Marty snorted, a smile making its way onto his face. “Yeah, good luck with that.” They sat in tense silence.
“You look really pretty when you’re focused.”
Marty clapped both hands over his mouth.
Casey choked. “You- you what?”
Marty’s eyes went wide. “I didn’t mean- I mean, I did mean it, but-” Casey’s entire face felt like it was on fire.
Marty dropped his hands slowly. “Oh my god. I’m worse at this than you.” Casey laughed despite himself, small and breathless. “You really are.”
Marty looked at him then, really looked, expression stripped bare by the lack of filters. The way Caseys warm hazel eyes looked with the light of the setting sun shining on them made Marty's heart skip a beat.
“You make everything feel less scary,” Marty said quietly, his voice sounding breathless, awe showing in his soft expression.
Casey’s breath hitched. “I didn’t even know I thought that,” Marty continued, looking away from Caseys gaze, than glancing back. “But it’s true.”
Casey’s voice came out barely above a whisper. “Marty…” Marty leaned closer without realizing it.
“Is this what you’ve been dealing with all day?” Marty asked softly. Casey nodded. Marty winced. “Okay. Yeah. That sucks.”
They laughed together, tension easing just a little.
But neither of them moved away.
---
By the time the side effects began to fade, it almost felt like a loss.
Doc announced the stabilization with far too much cheer, sending them outside “to give the timeline room to breathe.”
They sat on the steps, close but careful now.
Casey cleared his throat. “So… if it’s wearing off…” he said, his tone soft. Marty nodded slowly. “Yeah. I can feel it.”
A quiet settled between them, only the sounds of birds chirping, leaves rustling, and the sound of cars distant.
Casey picked at the seam of his jeans. “I’m sorry if I said anything that made things weird.” Marty laughed softly. “Are you kidding? That was the most honest I’ve ever been.”
Casey smiled shyly, looking down at his lap before glancing over towards marty. “You really think I’m… pretty?”
Marty didn’t hesitate. “Yeah. I do.”
Casey’s ears burned. “Oh.”
Marty nudged his knee gently. “Hey. Even without the side effects… I meant what I said.” Casey looked up. “You did?”
Marty nodded. “Guess the universe just got tired of waiting for us to figure it out.”
Casey let out a quiet laugh. “Took drastic measures.” Marty leaned in, slow and sure this time, making Caseys eyes widen slightly. “So… what do we do now?”
Casey’s heart pounded, but for once, he didn’t look away. “We try,” he said softly. “Carefully." Marty smiled. “I’m good at careful.”
Casey raised an eyebrow. “Liar.” Marty laughed, then leaned forward and kissed him, gentle, warm, and real.
No side effects required.