"Calumon zoom zoom, here a zoom, there a zoom..."

Calumon sang to himself as he cheerfully bounded down the tunnel he had just discovered, laughing non-stop as the graffitied walls of his new playground rushed past.

"Zoom zoom Calumon, here there and everywhere!"

Calumon suddenly stopped bouncing as he heard a weary groan from the shadows and saw a small figure rising slowly from the ground.

"Helloooo!" Calumon exclaimed, approaching the figure in the hope of making a new friend.

The figure let out a hiss. "Rats. I was hopin' ya wouldn't spot me."

"Nobody can hide from Calumon!" Calumon exclaimed, grinning at the mysterious person and letting out a laugh. "I am the best ever at hide-and-seek!"

The figure moved in a way that suggested the impatient flicking of a tail. "Stupid Cream-Puff," he grumbled. "Just go away and let me sleep, would ya?"

"Ohhhh," Calumon breathed as his eyes adjusted to the darkness and saw that the figure he had disturbed was none other than the notoriously bad-tempered Impmon. "It's you!"

Impmon snarled half-heartedly. "It's me. An' I'm not in the mood for ya unreasonable happiness. Go an' take it somewhere else, far away from me!"

Calumon folded his ears flat against his skull and tilted his head to the side, his eyes open wide in curiosity. "Would you like to play with me?"

Impmon scoffed and gave another flick of his tail. "No," he said, stubbornly folding his arms and turning his back on Calumon.

"Play! Play! Play! Play!" sang Calumon.

"No, no, no, no!" responded Impmon.

Calumon widened his eyes until they physically hurt to keep open. "Pretty please?"

Impmon glanced over his shoulder in annoyance, before conjuring a small flame from his fingertip. "No! Badaboom!" He flicked his index finger, sending the flame flying towards Calumon. Calumon bounced backwards, letting the flame fall at his feet.

"Badaboom! Badaboom! Badaboom!" Impmon continued, firing attack after attack at the giggling Calumon, who just dodged the fireballs as they came.

"Hee hee! This is fun!" Calumon declared, stretching his ears and leaping into the air. Impmon growled as Calumon jumped right in front of him, peering into the imp's irate face. "Yoink!"

Calumon deftly undid Impmon's red necktie and scampered off as the angry Digimon raced after him shouting curses.

"Get back here!" Impmon yelled, hurling another fireball down the tunnel and illuminating Calumon's way in the process.

"Ha ha ha! You can't catch me!" Calumon called back, leaping to the left as another fireball came shooting after him. Calumon let out a joyful laugh as the fireball hit the tunnel roof and provided a flash which temporarily lit up the tunnel.

Behind him, Calumon heard a strange noise emanating from Impmon's throat.

"Was that a laugh?" asked Calumon, dodging as a fireball missed his extended ear by about an inch.

Impmon gave a guttural growl. "No."

"I think it was!" Calumon declared, turning around and hopping on the spot as he realised Impmon was slowing down slightly. "I think you're having fun, Impmon!"

"Am not," Impmon insisted.

"Are too!" gloated Calumon.

"Am not."

"Are too!"

"I am not havin' fun!" Impmon snarled, raising both of his hands in front of him and conjuring swirling spheres of blue and red in his palms. "Summon!" he shouted, shooting shards of ice and a mass of sparks at Calumon, his irate expression distinctly contrasting with the perpetual smiley face on his torso.

Calumon dodged the attack, giggling, as Impmon scowled heavily.

And then Impmon collapsed into laughter.

Calumon watched curiously as the attacks stopped and Impmon doubled over, clutching his stomach, and howled with mirth.

"I knew it! You're laughing!" Calumon giggled, approaching Impmon without a trace of caution. "You're laughing! You're laughing! You're laughing!"

"No, I... I'm not!" insisted Impmon, as a fresh wave of giggles came over him.

"Would you like to play Calumonball with me?" Calumon asked, producing a large ball seemingly from nowhere and bouncing it on the floor.

Impmon gathered his composure and folded his arms. "No," he said, stubbornly, as his eyes followed the bounce of the ball.

"I know you want to play!" said Calumon, holding out the ball towards Impmon, whose gloved fingers almost imperceptibly twitched, as if to reach out for it.

Impmon adopted an expression which was clearly trying (and failing) to be a scowl. "Ya not goin' to shut up and let me sleep until I agree ta play with ya, are ya?"

Calumon beamed. "Nope!"

"Fine," said Impmon, in as grudging a voice as he could muster. "What're the rules?"

"No, no, no! You touched the wall while both of your feet were touching the floor! That means I get fifteen seconds of flying time!" Calumon shrieked, stretching his ears and taking to the air with the ball as Impmon let out an indignant huff.

"Ya touched the wall earlier and I didn't get any flyin' time!" he objected.

Calumon pondered this for a second, lightly touching back down on the floor in an unspoken time-out. "Well, you can't fly, Impmon! Of course that rule doesn't apply to you!"

"Now he tells me," Impmon muttered. "Well, what do I get, instead?"

"What can you do?" Calumon asked.

Impmon narrowed his eyes and held out his index finger, ominously. "I showed ya Badaboom earlier. Ya want another demonstration, Cream-Puff?"

"I've got it! You can use one elemental attack to bounce yourself off a wall!" Calumon decided. "But only if one or none of your feet touches the floor at the time."

"Well, if that's the case... Pillar of Fire!"

Impmon seized Calumon's ball and leapt at the tunnel wall, breathing out a jet of flame just before he hit it. Instead of colliding with the concrete expanse, Impmon ricocheted off and struck the ceiling, using his tail to bounce off until he hit the opposite wall and then landed gracefully on his feet in the centre of the tunnel, laughing the whole time.

"Wow," breathed Calumon, puffing up his ears and widening his eyes in amazement. "You hit the ceiling and both walls without touching the ground in between them! That means you win the game!"

Impmon tossed Calumon back the ball and grinned in a smug manner, but Calumon just left the ball lying on the floor.

"Yeah, I was kind of getting bored of Calumonball anyway," Calumon continued, turning his back on Impmon and bouncing away down the tunnel.

Impmon blinked. "Hey, don't ya want to play any more?"

Calumon giggled, without slowing down or turning around. "I knew you wanted to play really!"

"I... I do not want to play," Impmon shouted after him. "I only asked because I wanted to know if ya were goin' to let me get some sleep, now!"

"Night night, Impmon!" Calumon's voice responded, before his footsteps finally petered out and Impmon was left in silence on his own.

"Ugh," he grumbled, settling down on the floor where he had been lying previously and using the ball Calumon had abandoned as a makeshift-pillow.

The next morning, Impmon was woken up by the sun's light pouring in through the tunnel, illuminating the shadows with a rich, yellow glow, and he found that his red scarf had been draped over him in the night.

The scarf Calumon had never returned the day before.

Impmon tied the scarf around his neck and sighed. "Stupid Cream-Puff."

Author's notes: Just a short thing because tsundere!Impmon is my favourite thing and he and Calumon have the potential for the most adorable friendship in the entire franchise. Platonic Moe Couplet? Yeah, I think so. Potentially. :D

I apologise for my bastardisation of Impmon's accent; it was supposed to be an approximation of the Nyoo Yawk accent DSP gave dub!Impmon (because I grew up watching the dub and that is what I hear when I imagine the characters talking). I'm not convinced I got it right. Oh, well, this is why I'm not a voice actress.

This fic is currently a one-shot but I have a bad habit of returning to my one-shots without warning several months later and extending them. As such, this is technically complete, and I have no current plans to add to it, but I won't rule out the potential for more chapters featuring more of the bizarre rules of Calumonball in the future. And yes, "Calumonball" is a play on the "Calvinball" trope. :D