Very loosely inspired by the Terry Pratchett book Wintersmith. I stole the name and the idea of Summer Lady. Other than that, there's no crossover at all.

"Bunny," groaned Jack, "I'm dying." He was sprawled across the limb of an oak tree.

"Aaaah, suck it up, ya big baby," replied Bunny, sitting on the ground below. "You're not even covered in fur."

Jack groaned again for good measure, but Bunny remained unmoved. Why was he doing this? Why had he ever thought it would be a good idea? He was Jack Frost, for crying out loud. He wasn't meant to be around when it was—he couldn't bear to think about it—eighty degrees outside. Why, indeed, was a winter spirit gallivanting around in the month of June? The answer had begun formulating a couple months earlier…

Uncharacteristically, Jack Frost was thinking of summer. He hadn't missed it. Not for all of three hundred years, most of which he had spent chasing winter up and down the poles. Occasionally he caught the tail end of fall, and he always made sure to stay late into what was technically spring. He couldn't help himself; after all, weren't eggs supposed to be refrigerated? As for summer, it lay directly opposite him on the wheel of seasons, perpetually half a globe away. So Jack never felt any particular interest in what went on during while he was away.

But he had, before.

It was ironic that all but one of his memories from before had been of summertime. Exploring the forest, climbing trees, evening shadow-shows…and not much else.

"Isn't there more?" he asked when he returned his tooth box to the palace.

Tooth shook her head sadly. "I'm sorry, Jack. That's all we have." She rested a hand on his shoulders. "Just know that…those were the memories that you treasured the most."

"That-That's it?!" He tore himself away, suddenly angry. "So nothing else matters? My parents didn't matter? My life I spent with my sister wasn't important? Because even if I lost all those years of memories, it's okay, because those were the only ones worth saving?!"

"No, Jack…I didn't mean…" Tooth frantically tried to backtrack.

He thrust the box at Baby Tooth, who promptly floundered under the weight. Tooth scooped them both up, shielding them from the blast of wind as Jack took off.

He was going to get them back. Tooth didn't have them, so they had to be somewhere else. Memories never vanished. They were only forgotten. It was like how kids hid treasure under half-rotten tree trunks in the woods. When it got too icy, they'd stop coming for a long time. By the time the air had warmed up again, new growth completely covered the decayed log, but the treasure was still there, underneath. Once the kids ventured out, they gravitated toward their old haunts. Pretty soon, someone would see a familiar lump, and say, Hey, this was our secret place! And they'd dig out the crystals and dragonfly wings and admire them again.

It had happened the first time he'd heard his sister's voice. It set up a resonance inside him, and he'd felt snatches of images and sounds fluttering just below the surface. The sensation had been unsettling enough to draw him into Pitch's hole. He needed something like that, a trigger. Kids returned to their hideouts in the woods and unearthed the past. Well, he'd been hanging around Burgess forever.

But not all the time.

Maybe he needed to see it in a different light.

Which was how, against every instinct in his body, Jack Frost decided to revisit summer. It was awful.

"Feeling anything yet?" asked Bunny, glancing up.

"I think I'm melting."

"Don't be a wuss. It's just sweat."

"How do you live like this?" He was pretty sure things were even worse in the outback. No shady oaks, for one thing.

"I don't. I'm springtime, mate. I don't mess around with summer."

"Then why," said Jack, gritting his teeth, "are you still here?" It had been bothering him for a while. Upon learning what Jack was doing, lingering long past Easter, Bunny had invited himself to join Jack's mission. He was about as helpful as an elf.

"I thought you'd never ask," answered Bunny, grinning evilly. "There's someone I think you should meet."

"Who? A ghost?"

"Naw."

"It's not the leprechaun, is it?" said Jack, wondering who else was out and about this time of year.

"Come on, March was almost three months ago! 'Course it's not the leprechaun. You're going to love this one."

"So, are they coming, or…?"

"Any minute, mate."

Sigh. Summer was a stupid idea. Jack turned onto his stomach, letting his arms and legs dangle off the branch. One more minute, and if Bunny's friend didn't show up, he was going to Antarctica for sweet relief. (Fine, for some sulking, too.) And he wasn't coming back to Burgess until it was thirty degrees. He had almost succeeded in getting lost in a dream about wind, and the upper atmosphere, and the amazing kind of clouds which were actually made of tiny ice crystals, when something hit him on the back of the head, hard. It was so unexpected that he forgot to catch himself. Fortunately, Bunny was there for him to land on. All that fur made for some nice padding. One of the boomerangs was poking into his ribs, though. The other one attacked his skull.

Thwack!

"Ow!"

"Whadja do that for?"

"You hit me!"

"What, me? I'm sitting here, minding my own business" —Yeah, right, thought Jack—"and you decide to jump on me!"

"If you didn't throw this, then who did?" Jack picked up the oak apple. It had almost cracked in half.

"Ah," said Bunny. He inspected the baseball-sized sphere, turning it over in his paws. "She's here."

Jack tried to form a snowball, but all he could call up was a handful of mush. He spun around and pelted it into the mass of foliage anyway. It splattered on the leaves. "Where?"

"To slow. Over there," Bunny pointed toward the still road. Jack could see the heat waves rising off the surface, because no one was standing on it.

"What?"

"You see it?"

If he half-closed his eyes, the shimmer a vaguely human shape. As if it sensed him watching, the mirage vanished. A windowpane flashed with reflected light, then another. The flicker winked its way up the street, traveling away from them.

"What are you waiting for? Go!" Bunny urged.

"What, chase it?" Jack was incredulous. Chasing would involve moving. Even worse, it'd mean moving out of the shade. Another thought rose to the front of his mind. She's here, Bunny had said. A girl? "No!"

"She might have your memories…" intoned Bunny slyly.

Once the wind had died away, Bunny shaded his eyes with one paw and gazed happily at the figure skimming over the weather vanes. "Oooh, this is gonna be so good."

What did she look like? Jack didn't know. This was a major disadvantage, since chasing heat shimmer all over the town wasn't getting him anywhere. He lit upon a chimney to think. This person was almost better than he was, changing direction so fast that he'd nearly tripped in the air, which wasn't an easy feat. He'd burst out of an alley one time and caught an infuriating wisp of brown hair just disappear behind the corner. Time to switch tactics. When the Yetis had caught him, they hadn't bothered running around. No, Bunny had used a trap, appealing to his curiosity to lure him into his paws. Obviously, this girl was already intrigued by him; she hit first. And what did Jack Frost do better than stir up trouble?

If this didn't work, thought Jack grimly, it was blizzard time. To be truthful, after what he did what he was planning to do, he probably wouldn't energy left for anything more than some light hail. Perched on the awning over a lifeguard tower, he surveyed the sloshing crowd of children below. Every kid from miles around had congregated at the Burgess Public Pool. Forget City Hall, this was the center of town life at the moment. The corners of his mouth slid upward. She'd be bound to check out what the ruckus was.

"I prefer my water solid," he announced, and channeled every ounce of power he had into the chlorine depths. The surface of the water instantly became as still as a glacier. As one, the swimmers gasped for breath.

"Huh." He jumped down from the tower and dipped in a cautious toe. The pool was as cold as meltwater, but still liquid. Well, on second thought, it would have been a bad idea to trap all those people in a block of ice, anyway. He didn't fire a second blast.

Shock wearing off, a mass exodus out of the water began. Men and women in blue staff shirts instantaneously appeared, shouting and waving excitedly.

"I don't understand how—"

"Cold as ice—"

"Someone check temp control—"

Jack hopped back up on the tower and waited. Within minutes, he felt a change in the air.

It brought the smell of tall grass, and sweat. The metallic taste of warm rain, and sugary ice. The whir of cicadas and bicycle spokes. A brush of warm breeze. And, finally, above the gradually crystallizing surface of the pool, a shimmer in the air that resolved itself into a small, dark figure.

Jack squinted against the glare from the water. Waiting. Hands on her hips, she squinted back at him, outlined against the sun.

"Wintersmith," she said, clearly but quietly. "You're out of season."

He nearly fell out of the tower.

It was the right voice calling him by the wrong name.

He couldn't believe his ears. Slowly, holding tight to the metal ladder (which creaked at it cooled), he climbed down, watching her. With each step down he took, the glare faded a little more.

She frowned at the frost flowers that spread where he touched the ground. She stepped up onto the concrete lip of the pool (which immediately started steaming). The ice retreated. It was like a video of a growing vine played backwards. Now there remained only a few feathers of frost huddled between his toes. These, too, melted away as he stepped out from under the shade of the awning.

The look of astonishment on her face would've impressed North. The small part of Jack's brain which wasn't utterly frozen thought that he himself probably looked just as stupefied.

"Jack?" she breathed.

"—," issued from his gaping jaw. For the first time in three centuries, he felt cold. "I-I can't…you…your name" he whispered.

He couldn't even remember his sister's name.

She looked down. "It's okay," she said in the same quiet tone. "I'm Summer now."

To make things more clear, here's the theory behind this story:

After Jack died, his sister decided that he would have wanted her to keep having fun. Well, that was a little too hard in the winter, but in the summertime, she did her best to wonder WWJD (What Would Jack Do?) and masterminded devious adventures for the other kids. When she died (after living to a ripe old age and mothering Jamie's ancestors), the Man in the Moon preserved that bit of her. And so part of her soul, spirit, whatever, lives on as the personification of Summer. Kind of a counterpoint to Jack's brand of wintery fun.

Wintersmith is such a lovely name.

Update (6/5/14): Sorry, but Seasonals has been discontinued. I still look back on it fondly as one of the first fics I ever wrote, and have recycled some of the concept into an upcoming chapter of How Does It Feel.