97: Elves do not need catapults of any size, shape, or origin.
The bookstore wasn't nearly as good a research tool as North's library, because most people couldn't see him and thus freaked out when books appeared to read themselves. Still, he liked to people-watch. You could learn the most interesting things by seeing what books people read.
One woman wandered through the bargain-priced books, and stopped by the hardcover photography book that was essentially a National Geographic compilation of winter around the world. Jack loved that book. The NatGeo photographers had captured some of his best work.
She flipped through the book and made her way to the check out line. Jack drifted over, sending a faint puff of air to encourage her to turn to his favorite photo. She made appropriately awed sounds, and Jack drifted back, proud and satisfied. He bumped into a table behind him, and whirled around to steady it before anything fell over. The woman looked up briefly, but upon seeing no one, went back to her book.
Jack was about to fly away to find someone else to watch—maybe someone in the manga section, they were usually good for reactions—when he spotted a red-and-black book laying innocently on the edge. Jack couldn't help the devious smile as he read the title. He waited until nobody was looking and swiped it, slipping it into his hoodie pocket where it disappeared from sight.
He knew just who could use this book.
It would be epic.
The door slammed open, startling North into dropping his mini chisel. He swore in Russian, immediately bending down to pick it up and place it in its correct spot. His mini tools were an absolute chore to find if he lost them, but he didn't like the time it took to make a replacement. And anyway, he'd just worn the grip in.
"How many times must I say: knock first!" North shouted at the poor distressed yeti in the doorway.
The yeti gestured frantically and said something so quickly North could only make out 'elves' and 'catapult'. Those were not words North liked to hear in the same paragraph, much less the same breath. Forgetting his project, North stormed past the yeti and into complete chaos.
Peas, small stones, loose change, marbles, paintballs, bells, berries, and other vaguely round objects flew through the air. High elven war cries echoed above even the normal chaos of the workshop. Some elves enacted elaborate death scenes before falling still for a moment, then standing and finding a new target. Other elves lay where they had fallen, unconscious.
The weapons? Mini catapults made of all different materials and of differing sizes. North even spotted a trebuchet and a ballista shooting toothpicks.
"What is going on?" North roared.
Silence.
Then the elves started pointing at each other and chattering: explaining, making excuses, even threatening each other. But in that moment of quiet, North had heard the true culprit.
North stared up to where Jack Frost was clutching at one of his ceiling beams and laughing.
"Jack Frost, come down right now," North ordered. Still laughing, the winter sprite floated down. "What is meaning of this?"
"Oh, come on, North, that was hilarious!" Jack cackled, leaning on his staff.
"Elves do not need mini catapults! Look at mess!"
"It's not that much worse than the normal chaos around here," Jack pointed out.
"No. More. Mini catapults."
"Aye aye, sir!" Jack said, but his mischievous grin indicated he had something else in mind.
"I will be watching," North threatened.
Jack waved him off, flying up a level towards the kitchen. "Whatever you say, old man."
"Well, you only said mini catapults. Look, these are almost to size! And the elves had so much fun launching each other across the workshop."
"No."
"But it's a trebuchet, not a catapult! And this one's an onager. And this one is a ballista, it doesn't even throw stones!"
"No."
"You never said anything about hand-held weapons."
"No."
Addendum: Elves do not need weaponry of any sort, size, make, model, or origin. Ever.
In case you're curious, the book Jack found was Mini Weapons of Mass Destruction: Build Implements of Spitball Warfare by John Austin. He also made use of its sequel Mini Weapons of Mass Destruction 3: Build Siege Weapons of the Dark Ages.