Twilight walked into the library's undergrown breakfast nook, or at least managed the feat with as much added stumble as four generally-coordinated legs could manage when the mind directing them had deliberately traded off sleep for research. As it had turned out, the sleep would have been both more effective and somewhat less damaging.

She blinked several times, locating Spike on the fifth attempt. The little dragon was in the middle of making himself a typical early summer breakfast, which in this case seemed to largely center around imported turquoise with some sprinkles of crumbled amethyst. It was a fairly balanced meal, if you discounted the minor side effect of making his breath smell less like overheated charcoal and more like whatever that last ill-self-advised attempt at retuning her field's basic signature had produced.

Carefully, Twilight marshaled all her resources. Focused every bit of attention, intellect, and concentration she still possessed into speaking the single most important words of her life.

"Wake-up juice."

That seemed to be lacking something. Twilight considered the sentence from every angle until she figured out what it was.

"Now."

The little dragon, still working on the garnish, shook his head. "We're out."

The shock went deep and uncovered a previously-unsuspected, strictly short-term reserve. "Out? How can we be out?"

"Do you remember staying up until four in the morning -- and that was before we started running through the first part of the decontamination protocols?" her brother carefully asked.

"Sort of..."

"How do you think you got that far?"

Twilight sighed. "Okay..." Well, there was no help for it, not to mention a total lack of other options available. "Then... coffee."

Spike planted his claws on his hips before turning, had the half-narrowed eyes ready to go before ever reaching hers. "Twilight -- do you remember what you told me it would mean if you ever asked for coffee again?"

She frowned. "Something about... my having lost all reason, memory, sense of taste, priorities, and wanting to have my tongue ripped out of my head anyway?"

"Yeah, that was the first part. Anything else you'd like to add in there?"

Twilight considered. "Yeah. Coffee." And since it still seemed like such a natural follow-up, "Now."

"Twilight... how much of last night do you remember?"

It took more effort than she wanted it to and brought back things she'd been hoping to ignore. "Pretty much all of it through the explosion."

"Good. So... when you're up doing research until four in the morning when the intelligent thing would have been calling it quits before midnight and resuming when your brain is fully functional again -- but all you keep calling for are books and scrolls and somepony to go through sets of sixth-year notes... who do you think is getting all of it?"

"...you?"

"Oh, good," Spike replied. "Logic." Most of the sarcasm was implied, but still effective. "And... since we're completely out of yellow diamonds right now, how do you think I got that far?"

His sister carefully hazarded a guess. "...coffee?"

"Coffee," Spike confirmed. "All of it. So what's your next option?"

Twilight sighed and, on the third attempt, managed to plop down on the bench. "Breakfast. Just... breakfast. Can I at least get some orange juice with it?"

Spike smiled and got to work peeling the semi-spheres. "I did try to tell you how late it was getting. A few times, Twilight."

"I know... and I didn't listen... as usual... I'm sorry, Spike, but I thought I was just so close. Changing my signature..." Her field manifested as the usual pinkish hue, recovered a waiting brush from the tiny counter and began distractedly restoring her bangs, or at least as much as they could be given a certain lack of late-morning acuity and the hours-removed loss of the pink stripe.

"...has been on your mind ever since you saw Professor Chroma do it in sixth year," Spike finished. "And you still can't pull it off, which means there's nights when you decide you just have to make another attempt, and with your field strength at work, every single one of them ends with something blowing up. I've never been able to talk you out of any of them. Ever. Last night, I actually thought I had the words which would work. And they still didn't do it." The claws squeezed, and juice began to flow into the glass.

Twilight frowned. Certain portions of recent events had yet to be placed in their proper filing arrangement, making recovery less than certain. "What did you say?"

"I asked if you were trying to get a cutie mark in it."

The wince felt as if it was going to freeze in place. "And what did I say?"

"Actually... that's kind of when the first explosion went off..."

The little nook fell silent for a time as her brother worked, claws carefully arranging the foodstuffs which would keep his sister going through a late morning with the library closed for an unscheduled and extremely necessary basement fumigation, providing her with enough calories to function while stopping just short of the border marked Now That I Feel Up To It, Let Me Try That Again. It was an art form and there were still days when he wound up splashing most of the paint on the wall.

Eventually, he carried the laden tray over. "Start on that. I'll go see how the shield spell is holding." The little dragon walked out.

Twilight sighed, exerted her field again, surrounded a short length of twisted hay rope with glow and moved it to her mouth.

But I'm almost certain what I did wrong. Thoughtful chewing. Instead of pushing a little to one side or another... maybe I went laterally? Doesn't matter just yet: shields aren't great at confining fumes to start with and given when I put that one up, it's probably not going to hold much longer anyway. First thing we have to do is get that cleaned out before it leaks into the library and we spend two days trying to separate stink and paper, which is mostly going to just be me.

One rope finished: she started on a second.

So the air purification spell, if I'm awake enough to handle that... maybe it's designed to work on magma fumes for Spike's annual health trips, but I'm sure it'll get rid of -- whatever I did last night. And then we've got to pick up the fragments, recalibrate the oven again, plus if any of the notes survived, they have to be copied out with a lot of strategic triple underlining added.

Second rope distractedly consumed: her field fetched the orange juice.

Then maybe a nap. And after that, since the library's going to be closed anyway, we'll have the time to start all over aga --

The thought locked up all four legs and majestically fell over into a pool of local reality, splashing most of the contents out and leaving her briefly floundering in the scant hoof-height of fluid which remained.

The orange juice... wasn't.

It was in the clear glass. The container itself was securely held by her field. It hadn't quite reached her mouth, mostly because her eyes had finally registered the nature of the contents.

The orange juice was -- blue.

Carefully, Twilight set the glass down on the tray. There were times when viewing an item's color through a field created distortions for the true hues, and given that last night's failed experiments had involved changing her signature, it was obvious she'd temporarily done something to herself which made fully-surrounded orange register as something else, something which would no doubt clear on its own in a few hours and if it didn't, then that was the schedule for the rest of the day.

She released her field.

The orange juice sat within the glass. She could see tiny bits of pulp floating inside it.

The bits of pulp were also blue.

She leaned her head in, sniffed carefully. Orange juice.

Her lips tilted the glass forward just enough to let a tiny coating of fluid hit her tongue. Again, orange juice.

Back to the visuals. Blue.

Twilight smiled. "Very funny, Spike!"

Somewhere behind her, likely near the basement access door, "Huh?"

"The food coloring! 'Let me just see how she's feeling today,' right? You made one little thing in my environment different and you were waiting to see if I was going to obsess over it or start twitching or just go Discord all over the place? I'd like to think I've grown past that, Spike -- even if last night probably did give you incentive for throwing a quick micro-test at me..." She winced -- but only for a moment, and then the smile returned. "Okay... reality voucher received and cashed, all right? I won't work on signature distortion today: I promise."

The voice was getting closer now. "Twilight, I didn't put any coloring in your food today."

"Spike... I get it. I was obsessing. Scroll sent, lesson learned. Thank you... and I really mean that. You jolted me back before anything -- dollish happened." She was almost at the point where, Luna-passed PTSD cure or not, she could very nearly remember that without wanting to ram her head into the nearest wall. Twilight figured another six decades might be enough. "But honestly... blue?"

The little dragon walked back in. "Twilight... I didn't --" and caught sight of the glass "-- is that..."

Twilight blinked. Turned, saw his expression. Went back to the juice, which was incidentally still blue. "You... didn't?"

"It was orange when it came out..."

The siblings mutually stared at the glass for a while. The contents expressed their opinion of the scrutiny by defiantly maintaining their hue.

"Discord...?" Twilight carefully proposed.

"It didn't explode."

"It doesn't always have to explode."

"We haven't seen him since Fluttershy... well, whatever she did. But I don't think he'd start with a glass of orange juice."

"Maybe it's his calling card," Twilight suggested. "One small change to get our attention, and then we know he's -- coming by... later..."

Neither could completely repress the shudder. The Princess was willing to take the chance. Fluttershy swore he'd changed. Nopony else had any real faith in the so-called reform.

They waited. The glass continued to sit on the tray, patiently not exploding.

"Or it could just be magic," Spike suggested. "Did you check?"

Twilight frowned. "No... lack of wake-up juice... hang on..." She reached out with her senses, tried to get the feel of the glass -- and exhaled. What remained of her bangs shifted with equal relief. "And that's it exactly. Just a normal unicorn working. So somepony's pranking me."

Spike grinned. "Could have been worse. Any idea who?"

Twilight concentrated. "I don't know this feel... not the caster or the spell... actually, how is this operating? It's not an illusion: it's a physical change to the properties of the juice while still leaving it intact. It's changing the reflective index without altering anything else: that's a really neat trick! Do you think it's permanent? The thaums don't seem to be draining, but it's not as if I've gotten to observe it for all that long... I should go find the caster right now and ask how it's being done! There isn't quite enough here to study for any attempt to replicate... I'd need to watch it being done a few times..." With increasing excitement, "Do you think they worked it through the window? It's open a crack, you know: a field could get through. But maybe the caster wasn't aware of it. If they got around differentiation without even trying --"

"Twilight?"

"-- I'm going to need the first sixteen volumes over in the historical research record, no, make that the first eighteen and the last twelve, start indexing them by previous experiments and I'll need my third-year notes to cross-reference --"

"Twilight."

"-- what?"

"Would you like to set up the first experiment on a doll?"

The unicorn blinked -- then blushed.

"Um... I'm obsessing, right?"

"A little."

"And I should really just wrap up the basement fumigation before I start in on anything else?"

Her sibling folded his arms and silently nodded.

"Okay... let's get to work..."

Twilight finished her breakfast -- mostly: the rest of the orange juice had to be saved for further study. After that, it was an air purification spell which had been designed to assist in survival within a caldera, and then there was a great deal of extra cleanup to be done because the working hadn't quite fit with what was behind the shield. But in the end, they got it done.

Which meant that it was finally the scheduled time for obsessing over the wonderful prank spell!