Sadie: I can’t really picture Mycroft as a Little myself personally, but this prompt actually gave me an idea…so maybe this can qualify? 
¯_(ツ)_/¯ 

Hope you like it, anon!

“Yes, and what is it that

you

want?”

“Mycroft.”

Mycroft ignored his name and the tone of voice it was used in, and continued to stare down at his feet with a not-even-remotely-veiled sneer curling his lip.
“Well, why is he looking at me like that?”

“He wants you to play with him.”

The sneer deepened. “I don’t ‘play’.”

John raised an eyebrow. “…Seriously? You’re going to try to give me that, with a whole closet full of board games here, and you with a gameroom that at least 80% of the people on the internet would sell their grandmother for?”

Mycroft continued to scowl. He didn’t have an answer for that. He didn’t like not having an answer. He didn’t know that John knew about the gameroom. “You’ve got a big mouth,” he told his little brother, who was still sitting at his feet.

Sherlock didn’t answer…not verbally, at least, as Mycroft preferred, but hummed at him questioningly. Then he sat up on his knees and held out the lump of what looked like dirty, purple clay in his hands, offering it to him. 

“Aw, lookit,” John grinned, propping his elbow on the table and resting his chin in his hand. “Go on, Mycroft…play with him!”

“Games are one thing,” Mycroft admitted, albeit begrudgingly. He sniffed and sat back in his chair. “But I don’t do ‘crafts’.”

John rolled his eyes; this was not a worthwhile argument, and damned if he was going to let him spoil his baby brother’s good mood. “C’mere, love,” he said, reaching for Sherlock. “Mycroft’s being a pain in the…bum. I’ll do playdough with you.”

Sherlock wilted as John scooped him up into his lap from behind.

“ ‘Playdough’?” The name sounded as disgusting as it looked. “It’s clay.”

“Not quite.” John took the lump and split it in half, keeping one for himself and giving the other back to Sherlock, who slapped his on the table and began to mash it flat.

“It looks like it.”

“It’s different,” John said…there was a bit of an edge to his voice. But he was determined no to let the elder Holmes boy spoil anything with his smarmy attitude. “It’s…” He tried to think of a good reason, one that Mycroft wouldn’t rip to condescending shreds. “…softer.”

Mycroft stared at him flatly.

“And more colorful.”

He rolled his eyes.

“And it’s easier to sculpt.”

“So…child-friendly clay.”

John sighed as he worked the clay–playdough, in his hands to soften it. “Sure, Mycroft.”

Sherlock peeled his flattened purple pancake off of the table, then pinched it back into a lump and handed it to John with a grunt.

“What are you handing it to me for, hm?”

Sherlock tried to mash it into John’s fist with the other half, only succeeding with a small part…the rest was moulded to John’s hand.

“I take it you want me to do something with it?”

Sherlock nodded.

“What d’you want?”

Sherlock pressed his hands together and made a rubbing motion.

“A ball?”

Sherlock nodded again, excitedly.

“Ohhh, no.” John laughed, peeling it away. “I’m not rolling balls for you anymore…mine always come out egg-shaped, then you get cross with me for hours.”

Mycroft, who had been (surprisingly) quiet as he sat off to the side, watching, suddenly held out his hand. “I can roll one.”

Two sets of eyes sat and blinked at him, and he began to wonder why he’d opened his mouth. But before he could withdraw the offer, Sherlock was scraping all of his playdough together and shoving it across the table at his brother. “P’eathe!” he said, his dummy slurring his words. “P’eathe, My’coff!”

Mycroft wordlessly took the cl–playdough, and began to roll it between his palms.

John bounced Sherlock on his knee, beaming like an idiot.

“…Shut up.”

“Didn’t say a word.”

“You didn’t have to.”

Within the next hour, Sherlock not only had an entire army of miniature snowmen (all made with a trio of perfectly rounded spheres), but he had switched over to his brother’s lap. “What now?” Mycroft asked, resting his chin on Sherlock’s shoulder as he gazed over their battalion of  handmade ball-men.

Sherlock grinned and reached for one of the smaller snowmen on the outer flank ( ‘pawns’, Mycroft referred to them as)…then slapped his hand down over it, smashing it flat as he giggled like mad.

John roared with laughter at the look on Mycroft’s face as each and every one of his painstakingly crafted army were smashed by a maniacally

cackling toddler, who was taking great pleasure in his destruction.

“That’s the thing about playdough, Mycroft,” John said, chuckling and wiping the tears from his eyes as the other man shot him a withering glare.

“Smash it down all you want, but at least you can always build it back up.”