"... Well, we definitely should've given you more of a heads-up..." Shining Armour told his sister Twilight at her front door, referring to the impromptu foalsitting gig she'd had to endure nearly all day.
It had seemed like such a simple morning/afternoon schedule. Get some toys and cakes for a few sick foals in hospital, along with a book to read aloud to them. Twilight was just about to head out with her dutiful assistant Spike, when who should pop up out of nowhere than her somewhat beleaguered brother and his wife Cadence, who wanted Twily to watch their little 'bundle of joy', while they gallivanted off to attend some pompous art exhibition.
Being the self-professed 'best aunt ever' and not wanting to disappoint the stressed-out pair, Twilight agreed to foalsit baby Flurry Heart for a while, completely against Spike's sage advice. The parchment-carrying dragon's dire warnings of there not being enough time to watch the young alicorn and do everything on the list were completely disregarded, as a determined princess forged ahead with her plan of both attending to Flurry's needs and tending to the ill youngsters at the medical centre.
Except, thing hadn't gone exactly according to plan... a fact that Twilight was about to make her unsuspecting visitors aware of. In spades.
"Yes, you should have." She curtly replied, which led to Shining Armour and his wife exchanging a puzzled look.
"W-What do you mean?" Cadence enquired, a little shocked at her sister in law's sharpish tone. "We thought you'd love spending a bit of time with your niece today, because you're always going on about how you never see enough of her, as we live so far away, Did anything happen while we were gone?"
"Well, you could say that..." Twilight stared Cadence down sternly, keeping up her passive-aggressive demeanor. "But first, let's get back to your original question. Yes, I have told you a lot about how I'd love to have Flurry Heart round, so I suppose you could say that ones on me. Of course, that was before I found out..."
Shining Armour and Cadence held their breath, as Twilight struggled to find the right words in her extensive vocabluary.
"... What a whiny, misbehaving, spoiled little filly you're actually raising." Unable to produce a less-flattering description, she told it to them straight. "Your daughter can't sit still for one minute, never listens to instructions and creates mayhem wherever she goes. Oh, and why did you tell me she likes mashed-up peas... when she can't stand the stuff?! The evidence is now plastered all over my formerly pristine wall, if you'll care to see for yourselves."
With Cadence being so shocked at Twilight's uncharacteristic outburst it rendered her speechless, it seemed to be up to Shining Armour to respond to his sister's criticism. "Now listen here, Twily..." he frowned, disapprovingly. "You didn't have to agree to watch her today. All you had to do was say 'no', and we'd have been on our way. Also, you must realise that looking after an infant isn't easy. Just see how tired me and Cadance are now, to figure that out for yourself..."
"Ah, but you see that's where the manipulation comes in, isn't it?!" Twilight thought she had the stallion's game sussed. "You just knew that by appealing to my 'proud auntie' side that I'd capitulate and give in straight away. Very crafty, big brother! Just like how you got all the best toys when we were younger, by telling me I was so smart, I didn't need any of them! You won't fool me again with your psychological tricks! Plus, you've made the mistake of confusing your 'pride and joy' with a normal foal. Most babies, when they throw a bit of a tantrum, spit out their pacifier and yell for Mummy. Flurry Heart levitates an entire hospital... patients, doctors and all. So really, there's no comparison!"
Shining Armour gulped deeply upon hearing what mischief his 'precious' had been getting up to in his absence, while Cadence seemed to have recovered her tongue. "D-Did s-she r-really..."
"Well, I don't know why you're so surprised, considering what she nearly did to the entire Crystal Empire, but yes... it's true." Twilight told them both seriously. "And that's not even the half of it, but I'm too exhausted to tell you the rest today. My main point is though, that her behaviour hasn't improved an iota since the day your country was on the brink of destruction, thanks to her erratic mood swings. But who's responsible for this state of affairs? While it might sound like I'm blaming Flurry Heart, that would be a little harsh, don't you think? After all, she's only a small child, and is still learning and developing every single day. No, the ponies I'm holding accountable for her less-than-salubrious conduct today are..."
Another long pause. Cadance and Shining Armour must've known what was coming next, however...
"You two. I understand it must be a tough job, looking after such a high-maintenance foal but really... you have to put your hoof down more often. Don't always rely on a soft toy to calm her." This time, Twilight adopted a softer tone. "Not every second can be playtime, and occasionally you might have to be a bit strict to make her understand that. The only moment she listened to me all day is when I raised my voice, if you want to know what I mean. I know she's cute, and it might break your heart at first to discuss things like 'boundaries' and 'discipline', but I firmly believe that in the long run both you, and your daughter will be happier for it. Otherwise, growing up with her extreme power, I dread to think of the consequences..."
Twilight's words sounded pretty convincing, and Shining Armour along with his wife were actively considering them, but before they went any further, Cadence had a question. "Hang on. If I might ask, what makes you such an authority on the subject?"
"Well, personal observation for one..." Twilight proudly responded, before she couldn't help boasting her bookish credentials. "And I've read at least five good volumes devoted to foal-rearing. In 'How To Raise Your Filly' by Dr Bojack for instance, it says that between the ages of one and two, the smallest change in routine can have cataclysmic..."
"O-Okay, that sounds... interesting." Shining Armour glanced at his wife as if to say 'same old Twily', before turning back to his sister. "We might have to borrow that particular book sometime, but for now we have to go. The train makes no concessions for royalty if we're late, and we want to be back in time for when Flurry Heart wakes up from her afternoon nap. If you think you've been in the wars with her this afternoon, you ought to see what she's like when she's cranky..."
Twilight gazed at the deceptively adorable cherubic features of her slumbering niece, thinking how ill-matched they were for the true terror that lay beneath. "Okay. I'll put the book to one side for you, once Spike tracks it down. In the meantime, you will think about what I've said, won't you? Oh, and just one more thing..."
"Yes, what is it?" Cadence wasn't sure she was ready for any more surprises today.
"Here you go." Twilight deposited a small slip of paper in her hoof, with a large number written on it.
"What's this?" Shining Armour pondered, when his wife showed it to him.
"That's the cost of the clean-up bill today for the various messes your baby caused today, as I've already paid for all the 'apology' cakes..." Twilight grinned sheepishly. "There was the toy shop, the elementary, Sugarcube Corner, and the hospital. I already mentioned the hospital, I think? Anyway, I could've included the Friendship Castle in the final amount too, but as you're family I decided to waiver it."
"Very generous, I'm sure..." Cadence replied sarcastically. "Come on Shining Armour, we're leaving. 'Let my little sister take care of Flurry Heart', he says, 'we'll save some bits', he promises me. It would've cheaper to put her up at the Grande Hotel in Canterlot for a year, considering what she's cost us today..." moan
As Cadence magically dragged her sleeping foal and henpecked hubby away, Twilight couldn't help but worry that their parental methodology would still be just as lax the next time they crossed paths.
Oh well, can't say I didn't try, she thought, before taking a look all around her and realising something else.
Great, they left all these packs of diapers behind, and we didn't even need any of them today, either. Also, there's all those green vegetable stains on my wall still to clear away. What to do... What to do...
She was about to yell for Spike, before realising that her dragon friend was still on reading duty at the hospital. Hmm... so who can I get to...
"Starlight! I know you've been hiding up there all afternoon to escape co-foalsitting duty, you sneaky student! Well, now's your chance to make amends. Come down here this instant please, and bring a cloth. Dampen it first, though. Also, I hope you're good at lifting huge loads of disposable undergarments. It's all Friendship Lesson related, honestly..."
Author's Note
Another after-episode epilogue I thought of that I just had to write down. Hope you enjoyed it! 
