Author's Note/Warning: I am not a physics major and I certainly do not have any magic, so I don't know how well this experiment would work in reality. Probably not how it works here, where the effect is exaggerated against the scenery for comedy purposes. Potato guns can be hazardous and should only be built with adult permission and supervision, and never pointed directly at anyone. They should definitely, definitely not be overclocked and loaded with dangerous materials except by trained experts. Kids, absolutely do not try this at home.

Summer. The time when kids across the United States were let out of school and left to their own devices. When the total lack of responsibilities and the overbearing heat led to boredom. When there was never any shortage of idle hands to do the devil's work.

It was a Tuesday, or perhaps a Wednesday, the difference blended into obscurity when there were no events or duties to differentiate between one day and the next. It was Toriel's week to have Asriel and she always kept the house a bit too warm in the summer, an attempt to get her children to play outdoors more. So Asriel woke up splayed out on the bed with all the covers knocked off and his tongue hanging out of his mouth. He flopped out of bed and put on some light clothing before grabbing his phone and heading downstairs.

Frisk was already awake, sitting at the table with a bowl of cereal. Their mouth was full, so they nodded to Asriel once and only spoke when they finished chewing. "Morning, Asriel."

"Morning," Asriel greeted, raiding the breadbox to grab an onion bagel. "You been up a while?"

Frisk shook their head. "Maybe ten minutes? It's hard to sleep late when it's so hot." Asriel nodded an agreement with that. He toasted his bagel with fire magic and added cream cheese and sliced cucumbers to make a tidy sandwich. He poured himself a glass of milk and sat down at the table when his phone beeped with a new text message. Puzzled, he opened it up and read. He inhaled through his nose as he read and a smile crept onto his face.

"What is it?" Frisk asked, noticing Asriel's growing enthusiasm.

"That was Chara," Asriel said as he put his phone away.

Frisk raised an eyebrow. "They're up pretty early," they commented.

Asriel nodded, his face all business. "They've been working on the plans. I don't think they went to bed last night." He guessed this was true because Chara's text message was full of typos and sentence fragments. Chara was normally one of those weirdos who typed in complete, punctuated, and grammatically correct sentences over text or computer, so if their typing had gone so dramatically downhill they were probably sleep-deprived. "But they said they perfected the device and sent the plans over. Gonna download them now…" He looked over Chara's scribblings, scanned into the phone, while he ate one half of his breakfast. They were quite detailed, pinpointed exactly how much magic and what type would be needed to produce the desired effects. There were some calculations to the side where Chara attempted to determine how strong a material the 'potato' would need to be made out of, before they descended into furious scribbling where Chara gave up and decided on a material that would be way more than enough to handle the stress.

"Wow," he said when he finished looking it over. "They really went all out on this. The only new equipment we would need is a new bullet, but it would take four types of magic to test their theory out."

Frisk looked incredibly dubious. "They didn't really use four magics at once, did they?"

"Without using human souls, even I'm not that good," Asriel said. "Besides, you know how they are. It was a puzzle to them, all theoretical. They don't have the guts to test it themself. So who knows whether any of it actually works."

Frisk nodded. They stirred their cereal. Asriel chewed his bagel sandwich thoughtfully. They both swallowed. Then they faced each other with wide smiles.

""We gotta try it out!""

It started when Chara found the schematics for a spud gun online. It was not a terribly complicated bit of machinery and the parts could easily be bought with children's pocket money. It was a good afternoon project for Chara, Frisk, and Asriel, though they all agreed Toriel would never allow something like that in her house so they agreed to keep it at Chara and Asgore's. It was a pretty simple design, using a bicycle pump to compress air and launch a chunk of potato at high speed. It would have stayed a pretty simple design, if all of them had not had ideas on how they could improve it. Upgrade the loading mechanism to direct more of the gas into the projectile. Replace the bicycle pump with canisters of compressed helium. And then someone, somewhere, got the bright idea to throw magic into the mix.

The first idea was to simply reduce the weight of the potato, so the gun could push it harder. This resulted in their shot flopping to the ground only a few feet away. It turned out lighter objects experienced higher drag from air resistance, losing any possible speed boost almost instantly. So the thought went, what about if the potato was lighter at the moment it was fired but its weight were immediately restored? Would that not allow it to get both power and the ability to cut through wind resistance? This time when they fired, the potato vanished and the air was filled with the scent of unsalted french fries. It turned out making a chunk of potato go that fast would cause it to vaporize almost instantly. Even if they could make the gun stronger, they had run into a hard limit by their ammunition. An impasse.

But Chara was not done yet. The prospect of failure lit a fire under them; they would not allow it to end like this. There was more they could do, surely, they just needed some time. They promised to get this working and took the plans home with them. Asriel and Frisk had no idea what they were up to or what the result would be, but they knew Chara would think of something. If they were being egged on by their friends there was no limit to Chara's ingenuity. That was the last they heard of them until that morning.

Two days later, once Chara had the opportunity to sleep off their late night-slash-early morning session and Asriel had collected the last few pieces to complete the project, they all agreed to meet in Toriel's backyard. Frisk and Asriel set up the target while they waited. It was a standard bulls-eye paper target propped up with a thick sheet of metal behind it. MK was the first to arrive, dressed in a halter top and short skirt with a bow tied onto a head spike. Chara, still bleary-eyed from waking up, came with the gun. They nodded a greeting as they walked up to the group, only mildly surprised to see the non-Dreemurr there. "Oh? You brought MK?"

Asriel nodded. "We need four types of magic for the design to work: two uses of blue magic, one green, and one fire. That means four people."

"What's the point of all that?" Frisk wondered. "Even with only one of us using magic the popato blew up."

"Oh, we're not firing potatoes this time," Asriel said. He held up a small metal sphere with a divot on one side to slot into the loading mechanism of the spud gun. "We're firing this. Chara designed it and I talked Alphys into making a prototype."

MK took the bullet from Asriel with her tail. "So this is the new- woah dude! This thing's heavy!"

Chara's grin went from ear to ear and their eyes twinkled as they recognized the opportunity to educate. "Tungsten carbide, the best material in the world for projectiles. Density similar to lead and gold but stronger than steel, a melting point exceeding 5000 degrees Fahrenheit, and unable to be scratched by anything less than diamond. This is the stuff the military uses to make anti-tank rounds. If this thing can't survive our spud gun, nothing can."

This was normally the point at which a good kid would begin rethinking their decisions. After all, propelling metal at extremely high speeds had a very good chance of injuring anyone it struck, and even if it hit no one at all it could still give someone a fright from a near-miss. But they were all too excited to try out this new material to consider the potential ramifications of their mischief.

"So, run this by me one more time," MK asked. "What're we doing, and what's my part in it?"

Chara double-checked the specs. "You're better with green than blue magic, right? In that case we need you to hold the compression tanks together with binding magic. They're going to be under a lot of pressure, more than they were actually designed for, so without green magic they'll explode in our faces. Ree, can you handle the tanks?"

"Yeah," Asriel said with a nod. "That makes sense. So I'm… pushing the gas in them? Making it even more condensed and more powerful?"

Chara nodded. "Yes, exactly. Frisk, you will be in charge of the fire magic. As the gas gets compressed it will cool down, but we need everything to be hot for the gas particles to hit maximum speed. Meanwhile, I will reduce the weight of our, uh, 'potato'. In theory, the pneumatic force will be maximized by acting on a nearly-weightless object, and then as soon as it flies out of my range the weight will return and grant it the momentum to cut through wind resistance. That will give us maximum speed, power, and range from relatively humble equipment. Frisk, do you want the honor of being the one to fire it?"

Frisk shook their head. "You're the one who thought this up, and your magic's the easiest bit. I think you should do it!" Asriel considered arguing against this but thought better of it. If it worked they could all have a turn.

They set the potato gun up on a tripod so none of them would have to carry it. Each of the kids took up their positions; MK and Asriel at the far sides with Chara and Frisk in the middle. They were all wearing sound suppressing earmuffs to protect their ears, though someone had to help MK into hers and Asriel's ears had been stuffed into his like an overfull clothes hamper. Chara grabbed the gun underneath the barrel where the trigger was. "MK, you're first. Start us off."

MK nodded. "Fortifying canisters!" she shouted, her green magic flowing around the cans to solidify them.

Asriel was next. "Compressing propellant!" As his magic worked the gun began to shake. "Compression at 200% normal levels! How are the canisters, MK?"

"Ha! This is nothing!" she boasted. "Gimme more! More power!"

Asriel continued his work. Frost began to form on the outside of the canisters as the gas inside was squeezed into a much smaller area than it was ever meant to go. The gun itself rattled like a diesel engine was inside it. He struggled to make himself heard over the roar of the gun, "Compression at 300% normal levels!"

"That'll do!" Chara said. "Frisk! Start the fires!"

"Roger!" Frisk's magic could not be seen but it could most certainly be felt. Everyone flinched as a new source of heat erupted in the center of their formation, a space heater being flicked on during an already scorching summer day. The frost on the canisters melted and dripped, then steamed away. "Attack power full!"

"Preparing projectile for launch!" Chara shouted. The tiny nub of hardened metal glowed blue as Chara added their own magic to the mix. Perhaps it did not compare to the difficulty of the other tasks, but it was no less important. "It's ready! All systems green! Hahahahaha, our hearts are beating as one!"

Asriel was a little concerned about their half-sibling channeling Undyne, but it was too late to worry about that now. "Everything's ready, Frisk," he said, a little strain in his voice. "Start the countdown!"

Chara struggled to point the rattling gun at the target and their grip on the trigger tightened. Frisk intoned, "T minus five… four… three… two… one… zero! FI-"

Nobody quite remembered how the next moment played out. When it was all over the kids were splayed out across the lawn as the wreckage of the spud cannon smoldered. Pieces of the cannon rained down from above, and bits of pipe had scattered all across the lawn.

MK was the first to recover. She stood up, dazed, and looked around at the remains of the project. "SUCCESS!" she shouted, jumping into the air to knock her headphones off.

Asriel coughed, "That, ugh, was a success?" as he rose to one knee, then stumbled a little as he got to his feet.

Frisk held their head as they got up. "Wha… what even was that? What happened?"

Chara coughed and waved smoke away from their face. "The gun blew up," they said. "I guess even if the tanks could handle that kind of pressure the rest of it couldn't. So when I released the pressure by pulling the trigger everything went in every direction."

Asriel still looked uncertain. "I could have sworn I heard two explosions, though."

A hint of unease crept into Chara's smile. "I think that second one was a sonic boom. It happens when an object moves… faster than the speed of sound."

The kids looked at each other, then their heads swiveled over to survey the yard. A bullet is aerodynamically shaped to reduce drag. This not only allows it to fly faster, it keeps it flying straighter. Musket balls were notoriously inaccurate, as they would get buffeted by the wind from all directions, careening wildly through the air and causing unpredictable richochets. This fact burned itself into their minds as their vision panned over the yard to see what their sphere-shaped projectile had wrought. The target was completely untouched; instead the path of the ball could be traced by the wreckage it left in its wake. The shot completely destroyed the PVC pipe used as the gun's barrel, splitting it in two. It then burnt out a smoking furrow in the dirt which hopped and skipped in a lazy list right before veering sharply left when it hit a stone. The rock which was unfortunate enough to be in its path had a sizable chip taken out of its surface, still red-hot where it was struck. The bullet continued, slicing a line across Toriel's vegetable garden before kicking up sharply to smash through a second floor window. From their vantage point they could not see where the projectile ended up in the house, but they could only assume the damage did not end with what they could see.

A shape appeared at the window and a goat-woman peered outside. Toriel could not yet know what had happened but through mother's intuition she must have realized who was responsible. "Children?!" she shouted through the broken window.

All the children gave the signal at the same time: ""RUN FOR IT!""

The kids fled in all directions in a mad scramble. Though they were united moments before, now it was everyone for themself. They all knew they could not escape righteous judgment forever, and attempting to run would only make the inevitable consequences worse. But every moment they were able to avoid Ms. Dreemurr was a moment they were free and unpunished, and that was time well worth fleeing for.

AN: Seriously, do not try this at home.