A/N: This story is based on a cute prompt I received from inlovewiththeuniverse. I hope you enjoy!

A cardboard box filled with construction paper, markers, stencils, and other various crafting materials slipped from Amy's hands down to the second floor landing, for the third time that afternoon.

"I really should have thought this through," she mumbled to herself, as she crouched to gather the fallen objects, while tightening her fingers around the rim of a second box. "Don't you go anywhere," she warned it.

"Whatcha got there, Ames?"

The brunette jumped and lost her grip on the box. She sighed as it tumbled down to join its mate. "Cardboard boxes."

Penny rolled her eyes. "Okay, you're starting to sound like Sheldon. I didn't mean literally. What are they for? Are you moving and didn't tell us?"

"You'll be the first to know should we ever decide to move."

The blonde nodded then got on all fours to help retrieve the supplies. She turned a pill bottle-sized container filled with paper fasteners in her hands. "Are you hosting a children's craft fair?"

Amy plucked the container from her hand, placing it back into the box. "I'm planning a themed party for Sheldon's birthday. Well, not so much a party as a private celebration. I don't want a repeat of 2016."

"Yeah, the words 'Sheldon' and 'party' don't belong in the same sentence." She frowned at a bottle of white glue. "Is the theme grade school art class, because I don't see Sheldon enjoying that either."

"These are for, um...," the neurobiologist felt a flush creep up her neck all the way to the tips of her ears, "...for a top secret project."

"Ooh! Tell me!"

"I can't; it's top secret."

"For Sheldon, not me. I promise I won't blab."

"Sorry, bestie. I can't risk it. You don't exactly have a great secret keeping track record."

"Fine," Penny pouted. "Have fun with your project," she called over her shoulder as she trudged up the stairs.

"Wait!"

The blonde paused, excitement lighting up her face. "I knew you'd tell me."

"Nope. Mum's the word. Actually, I could use some help carrying this." Penny started up the stairs again. "Please? Sheldon will be home soon, and I can't let him see me with this."

Relief flooded Amy when her bestie returned to her side. She hated keeping secrets from her, but she'd put too much thought into this project for the surprise to be leaked. Plus it wasn't exactly something she wished to share with anyone but her husband. Her friends would probably consider her idea weird.

"How are you going to hide this from him?" Penny asked, when they reached the fourth floor landing.

"I was hoping you'll let me store it in his old room."

"Really? You're not worried I'll peek?"

"Don't think I haven't considered setting a booby trap. So, can I? Please? I need somewhere in close proximity where I can work on it. I don't exactly have many other options. I mean, there's Mrs. Petrescu's place, but then I'd have to haul everything down again, and that's if she agrees or even understands me..."

"Ames..."

"... not to mention, we barely know each other. I'd feel weird even asking..."

"Ames," Penny interrupted, "the room is all yours if you can find enough space. We've only been using it for storage."

"Oh, thank you, bestie!" Setting her box on the floor, she wrapped her arms around friend.

Over the next two weeks, Amy holed herself up in Sheldon's old room every chance she got - on new comic book night, when Sheldon invited Leonard over to play video games, and even during a girls' night in 4A where she spent half the evening with her friends and the other locked away with the project.

It was so strange being in that room after all this time. Sheldon's bed and dresser were still there, but all the other reminders were gone. The space would have been bare without all his action figures and comic books, but Leonard and Penny's collection of stuff filled the void.

She set down her scissors and flexed her fingers. Cutting through cardboard was hard work. A utility knife would have been more ergonomically friendly, but she wasn't keen on scratching up the harwood floor. Using the down time, she examined her progress. Only one more week until the celebration. It still didn't look like much, but it was starting to take shape.

The night before Sheldon's birthday, Amy put the finishing touches on her creations. Placing them on the bed, she stood back and admired her handiwork. It all turned out even better than she imagined. Other than her scientific achievements, this ranked among one of her proudest accomplishments. Sheldon would be so surprised and, she hoped, turned on.

When the big day arrived, Amy's plan was put in motion. Leonard would drive Sheldon home, Penny assured her it was fine to use her key to enter 4A, and Sheldon seemed blissfully unaware of the preparations. When the clock struck 12, she locked up her lab and headed to Los Robles. After several trips between the apartments, she set to work decorating.

It didn't take long for the transformation. Amy sat on the couch to admire her homemade creations placed strategically around the room. Was it too much? Instead of commending her on her hard work, would Sheldon be annoyed that there were decorations suspended from the walls? Then there was the main project sitting next to the TV mocking her in all its embellished cardboard glory. What if Sheldon found the idea silly?

"Breathe," she told herself. She needed a distraction, but neither reading, knitting, nor practicing her harp provided any comfort.

She approached the wall behind the TV and narrowed her eyes at one of the signs. From this close, she could see the small flaws in her cutting, stencilling, and coloring skills. Sheldon probably wouldn't even notice, and if he did, surely he would recognize how much work and love she put into it. Right?

"I shouldn't have come home so early. Now I'm just second guessing myself," she muttered.

Stepping away from the wall, she paced the tiny apartment over and over again. So what if Sheldon thought it was silly? Letting her creative side out had been very enjoyable. Very freeing. For that short time, she almost felt like a kid again, without any worries. No matter what happened, she would always have that experience to look back on.

Amy consulted her watch. Thirty more minutes until Sheldon was due home. She used the time to store the leftover supplies and take a leisurely bath. Just as she returned to the living room refreshed, the distinct sound of her husband's footsteps on the stairs permeated through the wall. It was showtime. She ran to the bedroom to get one more detail then scurried back and slipped the modified boxes over her head.

"I'm home!" Sheldon announced, as he tossed his keys into the bowl.

Amy stood before him, smiling nervously. "Happy birthday, husband!"

He turned to her, eyes widening. "Wow! You look... Wow!"

Amy tried to twirl around in her costume, knocking over the coffee table magazines in the process. "Sorry. I'll pick them up later. I can't bend right now."

He didn't seem to notice, his eyes roaming over her. "The detail is amazing. Did you do this yourself?"

She nodded. "Do you like it? I wanted to do something special for your birthday. I... I hope you don't think I'm crazy."

"You're not crazy at all, it's..." Sheldon tilted his head. "Is that my conductor's hat?"

"Y... yes. I thought it was a nice touch, but if you'd rather I not..."

He shook his head. "No, it's perfect. All of it. You combined two of my favorite things."

"Two?"

"You and trains. You look... Wow! I mean you dressed as a train... I have no words."

Amy blushed. "And not just any train. This is a Heisler locomotive, the fastest of the geared steam locomotives."

Sheldon's jaw slackened. "You remembered it's my favorite of that class. I know I've said it before, but you really are the whole package."

His head swooped down to hers. The bulkiness of the box between them proved to be a challenge, but he managed to angle his head into the cutout window.

She closed her eyes and savored the familiar softness of his lips on hers, the lingering hint of brownie, and his appreciative humming sounds. He pressed himself closer to her, his hands roaming over the cardboard. The one thing she hadn't considered when she built the train was the limitation of body contact. Hands trapped within the constraints of her costume, she did the only thing she could; she kissed him harder.

In response, his tongue prodded her. Without hesitation she parted her lips and moaned when he slipped inside. "Mmmmmmmmmm..."

They were both breathing hard when they finally broke apart.

"Shall we continue in the bedroom?" Sheldon panted.

Amy nodded her consent.

"You look so cute. I almost don't want to remove it. Almost."

He carefully lifted the train off her body and entwined his fingers with hers. With her free hand, she reached for the conductor's hat.

"Leave it on, just the hat, nothing else."

She glanced over her shoulder at the railroad crossing signs and tracks hung on the walls. He hadn't even noticed, but it didn't matter. He only had eyes for her.