To say that Twilight was feeling confused would have been something of an understatement. Oh, to be sure, she'd had her fair share of strange plans over the years, but she was usually the one giving them out, or thinking them up. Rarely did she have one of her close social circle use her as the one on the receiving end of some hair-brained scheme like this. And yet, here she was, sitting in her study while her lifelong colleague, Spike, stood beside her. The young dragon was, at this very moment, tying a bizarre-looking device to her foreleg, like a watch, though far from as normal-looking as that. It bore, right in its middle, a shining red gemstone, not unlike the kind Spike would have happily munched on at breakfast. And speaking of Spike, when the drake was happy that he'd secured the odd object to her, he took a step back and gave a firm nod, satisfied with what he'd done.
"There we go," he declared proudly.
Twilight blinked, looking down to him, then to the device he'd just put on her, before looking straight back to him.
"And this would be...?"
Spike shrugged.
"Just a little something I decided it was high time we got for you."
Slowly, Twilight arched an eyebrow.
"And that is...?"
Spike chuckled.
"It's the Twilight Alarm."
The way he'd said that made it seem like it was the most obvious thing in the world, yet as soon as Twilight heard it, all she could do was giggle.
"A Twilight alarm? What, you think I'm suddenly some natural disaster that everypony needs to be warned about, Spike?"
Spike smirked to that remark.
"Well...kinda, yeah."
Instantly, Twilight frowned, glaring down at the gem of the alarm.
"And what, pray tell, makes you think that something like this is needed?"
Spike gave her an incredulous look.
"Not to put too fine a point on it, Twilight, but you do have a history of going crazy over little things that don't go according to plan. Figured we ought to get something to make sure everycreature knows you're having a meltdown."
Naturally, Twilight looked a little indignant at that, looking away and giving a quick huffing sound.
"Humph! I do not 'go crazy' over little things, Spike!"
The young dragon opened his mouth to speak, only to have it shut again when Twilight reached forward and covered said mouth with her hoof.
"And before you bring up the want-it-need-it spell, please know that I've heard that excuse a million times already and I'm pretty sick of it by now."
After a moment, Spike shrugged, acknowledging her point.
"Fair enough. But that wasn't the only time. You seriously get worked up over lots of little things that don't really matter in the long run."
Folding his arms, he gave her a somewhat analytical stare.
"Like a certain trivia game or overdue library book?"
Hearing about some of her more recent examples, Twilight at least had the decency to blush. But, ever the professional, she utterly refused to allow such things to be viewed as anything even remotely as bad as Spike was making them out to be.
"For your information, I do not overreact to these things. I react exactly the right amount, thank you very much!"
Spike rolled his eyes, but said nothing as Twilight looked down to the device adorning her foreleg.
"Besides, what's this thing even supposed to do?"
Walking close beside her, Spike tapped the gemstone at the heart of the alarm.
"It monitors all sorts of stuff, like heart-rate, breathing frequency, you know, all the stuff that usually spikes when ponies stress out?"
Twilight afforded herself a quick giggle, patting her number one assistant on the head.
"And just where did you manage to make something like this? I didn't know engineering was one of your specialities."
Spike looked to his hand and started counting off his claws.
"Well, the basic theory was worked out by Sunburst, who took it to Torque Wrench to get the main setup going, and then we brought in a couple of other ponies in to fine-tune it, like AJ and Starlight. Oh! And I think we also got some of your old Canterlot friends for it too, like Moondancer, since they have a pretty good idea of what kinds of stuff sets you off."
Twilight's smile had vanished now, replaced with an utterly shocked look instead.
"...Exactly how many ponies have been told that I need an alarm to warn others of my apparently going nuts?!"
Spike counted his claws again, then muttered under his breath, before giving a somewhat sheepish look to her.
"You know...it's probably best you don't know the answer to that."
Twilight slapped her own forehead, then let out a long sigh.
"Spike...I appreciate you looking out for me like this, but I promise you, you have nothing to worry about."
Spike raised his eyebrow again, prompting Twilight to continue.
"I mean it. I may have had a history...okay, a long history of maybe going slightly off the rails when things stray from my expectations. But going this far is a little bit overboard."
Spike sighed.
"Look, just...just wear it for a day, okay? For me? If you can go one day without going crazy over little, unimportant things, I'll believe you and take it away, okay?"
It was a reasonable request, she had to admit, and so she smiled sweetly to him, giving him another friendly pat on the head before giving her answer.
"I accept those terms, Spike."
Spike smiled and nodded to her, glancing instead to her desk, which was currently covered from one side to another in papers from the school that had yet to be graded.
"So...you gonna get started on those?"
Twilight nodded proudly to them.
"Indeed I will. So..."
She gave a "shoo" gesture to him, which he immediately understood, nodding to her before turning around and making his way out of the room. Once he was gone, Twilight giggled over that entire encounter, then turned her attention to her papers. She sighed, ready to get down to the kind of work she loved best. But, as she reached for her quill and inkwell, she noticed, to her slight worry, that those objects were nowhere in sight. Confused, she looked in the drawers of her desk. No, they weren't there either. She gulped, turning around and looking on many of the surrounding shelves and tables, only to discover that they were similarly quill-less. Then, as she looked back to her unmarked papers, her eyes widened and a single drop of sweat started to roll down her forehead.
"Oh...oh no! What's going to happen if I can't grade these papers?! The students will be expecting them back any day now! What'll ponies say if I can't even fulfil the simple Headmare task of grading papers?! And the students! They'll spend their whole day stressing over the absence of their clearly-defined grades! They'll panic! They'll think I'm deliberately trying to torture them by making them wait longer than usual! They'll..."
But barely was she able to finish that train of thought when, all of a sudden, the gemstone on her wrist glowed brightly, and a booming voice called out from it.
"ALERT!!! ALERT!!! TWILIGHT SPARKLE IS GOING NUTS!!! I REPEAT, TWILIGHT SPARKLE IS GOING NUTS!!!"
Twilight stared down at her alarm, then, through the corner of her eye, she noticed a familiar figure leaning against the door of her office. Turning, she saw that it was Spike, who just so happened to have, in his claws, a certain quill and inkwell. After staring at him for a few moments, she coughed, blushing slightly and scratching the back of her head.
"Okay...maybe having this thing around might be worthwhile."
Author's Note
Let's be honest, having Twilight go nuts over little issues has been one of this show's most entertaining things over the years 
