This is a sequel to this: https://derpibooru.org/images/3491281

Back in Ponyville, it is now morning and everypony is going about their business. However, no pony is happy. They are upset and cross that their payback prank on Rainbow by pretending to be 'cookie-zombies' had backfired when the rainbow-maned mare had escaped thanks to some gold dust. As if they spend the whole night looking for her, and as a result, they were very tired and unhappy when morning came. But as well as being cross, they were a little worried as Rainbow was no where to seem

Derpy: Flying pass Smile, everypony! It's a sunny day!

Scootaloo: Worried It's not sunny, 'cause Dashie's not at her home or anywhere around Ponyville! I've looked!

Nyx: Also worried She's not in Cloudsdale either. Where could she is be?

Twilight: Sulking about the plan being ruined How could none of us had predicted that she had gold dust?

Applejack: Grumpy and annoyed Huh! I don't feel sunny! And neither does my tummy! It feels rougher than sandpaper!

Rarity: Also grumpy Nasty side effects from those dingy joke cookies! Hmm!

Spike: Annoyed And what's more, Rainbow got away with it!

Apple Bloom: Grumpy And when she comes back, she'll be boasting like there's no end tomorrow!

Fluttershy: Guys...

Pinkie: Well, then, we could dress Mare-Do-Well again to teach her a lesson!

Twilight: Frowns Pinkie, no. The last time we tried that, that rainbow-maned pony attacked us.

Fluttershy: Guys...

Applejack: Angrily And she got away with it that day too!

Rarity: Annoyed And we got into trouble! Honestly, how could ever time we think of a plan to teach Rainbow a lesson she keeps winning?!

Twilight: Cross I know! Either we need to really work more on our plans or she's good at sniffing them out! Oh, just wait until I get my hooves on her! I'll...!

Fluttershy: Fed up GUYS!

Fluttershy's loud shout made the group jump in surprise...and wince in disgust as Fluttershy accidentally sprayed them

Sweetie Belle: Wipes the spit from her face Say it! Don't spray it, Fluttershy!

Fluttershy: Sternly Never mind that! Dashie isn't in the wrong! WE are!

Pinkie: Shocked WHAT?!

Apple Bloom, Sweetie Belle and Nyx: Also shocked US?!

Rarity: A little indignant I beg your pardon?!

Applejack: Most indignant Excuse me?!

Twilight: In disbelief Fluttershy, what do you mean?!

Fluttershy: Sternly Our prank was wrong! SO wrong!

Spike: Cross What's the big deal?! We were trying to teach Rainbow Dash a lesson! Her pranks were totally out of control!

Rarity: And she made you cry, Fluttershy! Remember?!

Fluttershy: Still stern Yes, I do. And that's exactly my point. We were no better than she was.

Scootaloo: Cross Yeah, Fluttershy's right! We are all just as bad.

Twilight: Matter-of-factually No, we are not. You do something bad, you face the cons... Trails away Face the...

But Twilight was cut off when Fluttershy gave her and the group....the stare

Fluttershy: Staring hard-Pointedly Oh, really? Well then, if somepony steals something from you, or makes fun of you, you have the right to do the same thing to them? Mm?

Twilight: Now having lost her nerve I...I...I...I...

Suddenly, it dawn on everypony...

Nyx: Now feeling guilty Uh-oh...

Rarity: Trying to find something to say But...but...she...

Fluttershy: Sternly It doesn't matter. Even if we wanted to teach her a lesson, we did it the wrong way. What sort of example is that to set for these fillies? Gestures to Apple Bloom, Sweetie Belle and Nyx who are now feeling guilty as Scootaloo glares at them We should be ashamed of ourselves. Hangs her head in shame I sure am...

Everypony was feeling guilty, and not just because Fluttershy was sad. A chipped tooth could be fixed, a strained back healed in a couple days, and as demonstrated by Fluttershy, that dye from those cookies could be wiped away with ease. While their own pains certainly mattered, they had forgotten Rainbow Dash's mattered too...

Twilight: Sad and ashamed Fluttershy's right... We said that a prank isn't good if you're the only pony laughing... Now look at us... We knew Rainbow Dash wouldn't like this prank, or think it was funny, but we didn't take the time to think about exactly how bad she would feel either... And making somepony feel bad like this is never okay... It's no wonder Rainbow's run away...

Rarity: Upset We'll have find to Rainbow and say sorry to her...

Spike starts moaning and starts crouching over, holding his belly

Twilight: A little worried Spike?

Spike: Unwell Ugh... I think I ate too many of those cookies too fast...

Rarity hugs her dragonfriend and rubs his head

Rarity: Aww, poor little Spikey-wikey. Suddenly starts to feel a little uneasy herself, wincing and feeling a bit of pain in her own stomach Ooh... Now that I think about it, the excitement of it all made me gorge myself. Oooh, so unladylike...

Applejack: Sickly Ohhh... I feel fuller than a gulley after a monsoon...

The group all start feeling the effects of eating too much too fast... Even other ponies nearby are also looking unwell and green

Twilight: Unwell Ohhhh.... I think we should that we get some rest, tell everypony about how bad our prank was and then we'll send out a search party for Rainbow.

The Group: Sick Okay... Ohhhhhhh....

They then all head back to their respective home, all feeling really sick and green in the face

Nyx: Sick and green Mom... Is.... Ohhh.... Is this what they call "actions have consequences"...?

Twilight: Looking even more sick Ohh... Yes, Nyx... And it is us who have to face the consequences for our selfish plan... Oh, I hope we can find Rainbow soon... If anything happens to her, I'll forgive mysel.... Suddenly holds her belly in pain as she goes even greener Oh, no...!

Twilight speeds off to her castle, looking like she's about to throw up!

Nyx: Worried Mom! Runs after her

References:
https://archive.org/details/thomas-and-the-magic-railroad-uk-dvd-2000
https://www.fanfiction.net/s/12421585/5/What-Is-A-Person-Worth
https://youtu.be/yxzYnjXFh6Q?si=SJjss323hPhsaFfw
https://www.fimfiction.net/story/363887/1/28-pranks-later-alternate-ending/how-it-could-have-happened
https://youtu.be/ICBHy8hUxNw?si=U66R0ek45aCpzklW