Warmth.
Tank stirred as he felt the warmth all around him, easing his body out of torpor. His stomach ached with emptiness. So did his heart. He pushed against the soil. Soon, he would be with the pony who would fix both of those problems. Once his claws worked past the dirt, he would break through to...
Rock?
That wasn't right. Tank had been more than half-asleep when he'd buried himself in the winter, but he definitely would've remembered a rock right in front of him.
Still, it wasn't going to stop him. Tank pushed his head against the dirt. It resisted at first, so he kept pushing. His lungs were starting to burn by the time the dirt gave, but give it did. Sweet air swept over his beak, and he blinked in the light of day. Aside from the rock, the park was largely as he'd left it.
The rock only came up to the bottom of Tank's shell. Once he scraped out a little room to maneuver with his rear claws, he clambered over it easily enough. It was a good rock, flat and sunny. It would make a nice place to wait for Rainbow. Still groggy, Tank shut his eyes.
Soon enough, he heard the sound of wings. A smile crept over Tank's beak. He was patient, but he knew the wait must have been horrible for Rainbow. Well, now it was over. He looked forward to flying again.
"All right, you three, I've given you plenty of warnings. Now you... Tank?"
Tank opened his eyes. That voice wasn't Rainbow. It was Twilight Egghead, staring at him with her mouth hanging open. Tank stared back. Twilight probably knew where Rainbow was.
The two stayed like that for some time. Finally, Tank gave an inquisitive croak.
Twilight shook herself. "This... This is..." She took a deep breath. "I need to call in the girls." Her horn glowed, getting brighter and brighter.
Tank pulled his head into shell. He'd left his sunglasses at home, in the special room Rainbow had made for him. Once he heard a loud burst and the purple light stopped shining through his neck hole, he stuck his head back out, smiling again. Now Rainbow would be here.
Tank's smile fell. Rainbow wasn't here.
On Twilight Egghead's right was the Pinkie Pie, who had gone still and silent. Well, as still and silent as the Pinkie Pie ever was, which meant a great deal of blinking and strange, choked sounds. Tank didn't understand her, but according to Gummy, she was as wise as she was mad. Of course, the same could be said of Gummy.
On Twilight's left was... well, the orange fur and hat made her look like Ayjay, but she was as wrinkled as a tortoise. She was also gawping at Tank, and glaring at him as well.
The Pinkie Pie untangled her tongue. "Is that really—?"
"It is," said Twilight.
Ayjay simply snorted.
Twilight frowned. "Tank, can you understand me?"
Tank nodded. Rainbow spoke quickly enough that a pony like Twilight Egghead was easy enough to understand.
Her frown stayed. "I... I don't know how to tell you this, but—"
"You're really late for your party," said the Pinkie Pie.
Twilight frowned at her. "Pinkie!"
"Ain't like he deserves a party after what he's done." Ayjay's voice came out rough and bitter.
Twilight turned to her. "He couldn't help it—"
"Don't mean it ain't his fault."
Tank looked back and forth and gave another questioning croak.
Twilight sighed. "That first Winter Wrap-Up... well, you just didn't wake up. After a week, we started trying to force you out of hibernation. Physical stimulus, magic, Fluttershy asking nicely..." She shook her head. "Nothing worked. And we were thorough."
Pinkie nodded. "I even shot you out of a party cannon."
"As I said, thorough."
Ayjay doffed her hat. "Rainbow didn't give up on ya, even when th' rest of us did." She rammed her hat back on her head and glared at Tank. "Fat lot o' good it did 'er."
"Ayjay," said Twilight, "please—"
"Zip it, Twi. Ah'm gonna say mah piece." Ayjay stomped closer, barely any faster than Tank. "That mare wouldn't give up on ya, Mr. Sleepytime, but she sure as sugar gave up on everything else! She gave up her friends, her dreams, the sky itself! All 'cause you had t' sleep fer one hundred princess-damned years!"
Tank blinked. He felt his beak fall open.
Ayjay spat at his claws. "Send me back home, Twilight. Ah got a farm t' watch over, an' Ah'll be all day gettin' back on mah own."
"Ayjay, please, be reasonable."
She whirled on Twilight, wincing at the sudden movement. "This is me bein' reasonable! Send me back if ya don't wanna see what me bein' unreasonable is!"
Ayjay vanished in a burst of light. Twilight sighed as her horn dimmed. "I'm sorry, Tank. It... Well, it hasn't been easy for us. Some more than others. When Rarity—"
Tank found himself being lifted up and moving at supertortoise speeds.
"Pinkie, what are you doing?"
The Pinkie Pie answered from above Tank. "He wants to see her. He should."
She set Tank down on the grass, facing another rock. It presented a flat surface, engraved with a familiar cloud and lightning bolt.
"Pegasuses don't usually get buried," said the Pinkie Pie, "but she knew you'd wake up one day. She wanted to be there when it happened."
Buried...
Tank looked down. Grass, and beneath it, dirt. He narrowed his eyes and scraped away the grass with a claw. The grass didn't matter.
"Tank?" said the Pinkie Pie.
He kept digging. The dirt didn't matter.
"Tank..." said Twilight Egghead.
Their voices didn't matter. His hunger didn't matter. He didn't matter. The only important thing in the world was beneath him. She was waiting for him. He would not keep her waiting any longer.
"Tank."
He was lifted off the ground, wrapped in light. He thrashed, claws waving, beak snapping. The time for patience was over. He would deal with anyone who kept him from Rainbow, then return to her.
Tank was spun until he faced a larger pony, one with sparkles in her mane and a moon around her neck. She smiled. “So like your mistress. A hard shell hiding a soft heart. Your devotion does her proud.”
He hissed at her.
The moon horse's smile only widened. "Peace, good tortoise. I am not your enemy, and things are not as they seem. This is only a dream."
Tank blinked. A dream?
"I must say, I have never before seen a beast of the fields have a nightmare so terrible that it required my personal attention. Still, you do hail from Ponyville. I do not know if it is some fell energy from the Everfree, the proximity of Discord, or a legacy of my darker self, but I seem to spend more time soothing that town than the rest of Equestria combined." The moon horse looked around. "And you do show unusual wisdom, recognizing Pinkie Pie for what she is."
She turned Tank to see Twilight and the Pinkie Pie frozen in place. The Pinkie then turned and waved. "Hi, Luna!"
Luna the moon horse sighed. "Lady Pie, I know we do not spend as much time together as you like, but we have discussed intruding on others' dreams."
The Pinkie Pie pouted. "Aww... fine." She returned to her earlier pose.
"Though the Element has returned to the Tree," said Luna, "we both still do the work of Laughter. She brings joy to a town. I chase fear from a kingdom." She smiled. "I believe I see why Rainbow Dash likes you so much, Tank. You are an excellent listener."
Tank gave a small smile back.
Luna set him down. "In any case, rest assured, in every sense of the phrase. Less than a month has passed since the longest night and the beginning of winter. Rainbow Dash is alive and well, and her reunion with you figures largely in her own dreams. And should you not awaken come the spring, I shall personally return you to wakefulness." She dipped her head to him. "For now, I wish you sweet dreams during your long rest."
The propeller hummed above Tank, the sky was clear of any buildings that might jump out in front of him, and the lettuce fields stretched as far as he could see.
Rainbow drifted by, lounging on a cloud. "Don't worry, buddy. I'll always be there for you."
Another tortoise buzzed by, a coy smile on her beak. She gave Tank an affectionate, gentle collision and a coquettish wink.
Rainbow chuckled. "Now go have fun with Ironclad. Just remember, you can't bury eggs in a cloud house."
Author's Note
A bit late? Of course it is. It's a Tank story. Did you really expect me to write it quickly? 
In any case, Tank presents an interesting twist on the longevity blues; it is entirely possible that he could outlive Dash. Given the theme of grief in "Tanks for the Memories," this seemed like an interesting reversal. And Ponyville probably does make up a significant portion of Luna's nightly workload. I cut a scene where she confronts Discord about his possible responsibility for the phenomenon. I think I diluted the initial tone of the story enough as is.
Also, Tank learned the names of Dash's friends from Dash herself. And from Gummy, disciple of the Queen in Pink, long may She party. 
