Copied from my Charms midterm. I would never play the following prank in real life, and I don't want to advocate pranking anyone PAs. Don't read this at night if it's easy to scare you!

We
had been planning this day for ages. It was finally our time to act, to
react to all that unfairness that we had experienced in the last couple
of month. All that unfairness that had been caused by you. It was just
not fair. Chris and I had always handed in our work at the same time,
double-checked all our references and proof-read each other's essays -
and yet, only one of us got them back in time, whereas the other one was
forced to wait for ages and ages. And when we - finally - got both our
essays back, there were always differences in the percentages we
received for our work. Huge differences. Not just small ones that could
be explained by minor mistakes. We checked our essays together, so the
language should be similar. We did our research together, so the content
would include the same aspects. We double-checked that we never
identified ourselves. And we even kept the word limit. So how was it
possible that our grades were that different, like more than 20% at
times? This was not fair, this was pure arbitratiness, capriciousness!
And we were sure of one thing - of the person whose fault it was. It was
all your fault. Yours alone. And we would get our revenge. Tonight.

"Emma,"
I heard Chris whisper from her bed. It was really handy that her bed
was directly next to mine, we could easily communicate without raising
any suspicions from our dorm mates. Not that they would try to overhear
what we were up to, in the early hours of this morning. "They're asleep.
It's time!"

"Finally!", I hissed back. It had
taken them ages to fall asleep tonight. But everything was organised, we
didn't have the time to change our plans. This evening's thunderstorm
had nearly destroyed the planning of a month! "Lumos!" Softly
saying the incantation while moving my wand in a counter-clockwise loop,
I was careful not to wake anyone while I was gathering my appliances.
To my left side, I saw Chris doing the same.

We
only had two bags to carry, so it wasn't too difficult to move them
quietly. Especially as we were careful not to disturb their contents too
much. It wouldn't do to have the surprises come down on us. Quietly, we
were sneaking out of our dorm. As soon as we were on the staircase, our
dorm's door safely closed behind us, we were hurryingly discussing our
plan in whispers. Nothing should go wrong after all.

"Did
you manage to find the last...", I asked, looking at Chris. It was
still unsure whether we would have to improvise when we last discussed
our plan. But the more, the better!

"Yes," Chris interrupted, grinning sadistically. "And you collected your part as well, didn't you?"

"Of
course," I replied indignantly. How dare she suggest that I would not?
"Are you sure that we won't get into too much trouble for this? I mean
to say, ..."

"Don't worry, we'll be fine. No one
will know it was us anyways!" Well, hopefully no one would. We couldn't
lose that many house points, not that shortly before the house cup would
be awarded! It would take all our chances of winning away!

Quietly
and carefully, we tiptoed to your office. We were actually planning to
prank your quarters first, but couldn't think of how to organise it
without implicating ourselves. So it had to be the office. Well, that's
good enough, as long as it wouldn't be too obvious. We were hoping that
it would be unlocked, though we didn't believe in it. But both of us had
practiced unlocking charms in our free time. And tonight should be a
good night after all - as you were called away on a quick note as there
was some kind help needed due to a pranking spell gone wrong. What a
great plan it was, almost worth being hexed by Chris! And you didn't
have a chance to return to your office that night, you never did on
Fridays. If you had to leave in a hurry, it would be more likely that
you hadn't locked your door too carefully. And after all, you had always
told us that the only thing anyone would ever steal from your office
would be your candy supply. You never left anything else in the room,
always charming everything back to their proper place. You wouldn't see
the need for a complex magical lock.

"There we are," Chris hissed. "Will you try, or shall I?"

"You,
please!", I whispered. The whole thing was racking my nerves. I
couldn't believe we'd actually dare doing this to you, but honestly, you
did deserve it.

Slowly, Chris took out her
wand, a look of deep concentration on her face. Though it was not
necessary, I took the time to focus, too. The door would open, like we
had seen it open that many times before. It would open. It would let us
pass. Drawing a backward S shape with her wand, I heard a determined
Chris trying to open the door. It wouldn't budge though.

"You try!" And so I tried the same, focussing, minding my wand movement, pronouncing Alohomora as carefully as possible. And yet your office door wouldn't budge an inch.

"Maybe if we do the charm together? On three! One, two, three, Alohomora!"
For whatever reason, our combined effort worked. We had managed to open
your office door. And now, there were two devious first years in your
rooms, with bags full of nasty surprises, unsupervised, and willing to
make you suffer. You'd never dare to say again that first years were not
creative enough!

Quickly, we dropped our bags.
There it was, your precious candy box. "Careful not to leave any
fingerprints!", I murmured as Chris was approaching it quickly.
Honestly, that girl had no common sense at all! After all, we did not
want to be identified and have to fear the wrath of both our house and
you!

"You levitate the lid then, and I'll do
our surprise, right? You could hold that charm a bit longer than me."
Well, she was right, but I was scared of messing it up.

"Wingardium Leviosa!"
Twin whispers, accompanied by swishs and flicks. I didn't even think of
using an older version of the charm, Levioso would have done the job as
well! Focussing on the flying objects and where they were meant to go,
we quickly set to work. It wasn't only your candy box that was pranked.
No, we also left some surprises at other places in the office. You
wouldn't know what hit you. And we would certainly be at your office
tomorrow morning, asking some questions about our current assignment. We
had to see whether it worked! Quickly collecting any evidence that we
had been there, we tiptoed back to our dorm. It would be a good night
indeed.

And as it turned out, it would be an
even better morning. Apparently, you didn't like thunderstorms, so you
were quite tired anyways. Then, someone got the last bit of coffee right
under your nose. So you didn't even have coffeine to keep you awake.
And finally, when you would set down in your office, you would be
covered in bright green goo - magically resistant bright green goo, that
could neither be spelled away nor transfigured in anything else. To top
it of, we had collected spiders that were attracted to that very goo.
As we were approaching the office, we were snickering. We could
anticipate the scream of terror you would emit, and run for our lives as
we were 'poor little scared firsties'.

And we would have had our revenge. You would be punished. And we would continue to do so, whenever it became necessary.