A Different Kind of Battle
Season 6

In hindsight she should have maybe foreseen that the "gag gift" she'd bought would be the biggest hit. This was Castle after all.

She'd wanted to buy him something special, this being their first Christmas engaged and after a turbulent year she'd wanted to spoil him a little. He'd been moved by all her gifts and she was pleased with herself over how she'd managed to find Martha and Alexis incredible gifts too that they'd also loved. But the marshmallow launchers she'd bought for both Castle and Alexis on a whim would be the most memorable part of Christmas that year.

They'd both laughed when they'd opened the gift and looked at each other with glee. With the sweet tooth Big Castle and Little Castle had, she'd thought they'd get a kick out of them. It started out innocently enough. Plans to make cocoa, joking that whoever could land their marshmallows in from the living room got the bigger mug, then Castle had talked Alexis into trying to shoot a marshmallow into his mouth from across the room. As it hit him in the chest Alexis dissolved into laughter and told him she knew it wouldn't work.
"You would think it would be hard to miss a target that's always open," Kate joked with Martha who laughed, nodding her agreement as she watched her son and granddaughter. Castle opened fire on Alexis when she turned to join in with the teasing and so began the battle. Castle dropped behind the sofa as Alexis ducked behind a beam, diving in and out of their hiding spaces to take aim at the other.

Martha tried to intervene but after years of laser tag, knew better than to get in the way. Kate tried a little more valiantly to tame the battle but she'd heard the tales of the wars these two had waged over the years and when Martha beat a hasty retreat to the kitchen, she joined her, pouring them each a glass of wine.

They watched on amused, Kate rolling her eyes at the childish threats her fiance was making at his daughter. Kate chatted with Martha until a stray marshmallow struck her in the back. Castle stopped, not sure what she would do next as she turned to glare at him
"Now, Beckett, that - that was an accident. That would have hit Alexis had she not ducked," he tried to explain.
"Don't blame me!" Alexis warned him.

Kate moved across the room, a smirk gracing her lips as she raised an eyebrow at him, watching as he started to move away, attempting to keep distance between himself and his fiancee. "Beckett, come on. The trigger on this thing, it's highly sensitive and… and… I would never…" She dove at him, tackling him onto the rug and wrestling with him as she pinned his arms, presenting him as a target for Alexis who took him down without mercy until all three of them were laughing.

She sat on top of his thighs, looming over him. "Learn your lesson, babe?" Kate teased, looking down at him with mischief in her eyes.
He grinned up at her, not entirely unhappy with this turn of events. "You'll never defeat me," he said as he managed to topple her off and jump to his feet. Kate gained control of his launcher and hit him square in the back of the head as he tried to make a break for the kitchen and use Martha as a shield. "I don't think so kiddo, you're outnumbered and you're not dragging me into this," Martha told him, sipping from her wine glass.
"You win, Detective, daughter."

"Thanks Kate, these are fun," Alexis told her, exchanging a high five after her father conceded defeat. Kate smiled, proud and beyond grateful to be with this new family she was in love with more and more each day. Kate pressed a kiss to his lips quickly, before they all returned to the living room to watch a movie together.

AN: Written as part of the Castle Secret Santa 2018 Tumblr event.