This story was inspired by this comic by swaetshrit.

A pony is the collection of her experiences. But what if those experiences never occurred? As Pinkie's reality falls apart and gives way to a much less party-filled world, she will have to ask herself: Who was I, who am I, and who should I be?

The original versions of the first two chapters can be found here.

If you haven't guessed, this story is meant to be bad. If you guys like it, I'll revise it and make it better. But I originally wrote this because I was bored.
The Mane 6 get turned into fillies due to a spell gone wrong. Twilight has a minor mental breakdown. Hilarity ensues.

Rainbow Dash thought it was over. Her limbs were burning, the straps keeping her pinned down tight, her cyan fur ruined by the stench of her own blood spilt by Pinkie's hand. She closed her eyes and waited for the last strike that would end her life. But then, there was a banging on the door...

Beginning in a psychiatric facility, the pink earth pony falls victim to faulty doctoring and her mental health deteriorates. This story is based on "Cupcakes," only in this universe, it never happened. It was all in Pinkie's mind. Now she's back in reality and her friends try desperately to help her recover. However, through this, her relationships with the rest of the mane six are altered for good. Now she must rediscover who she is and who her friends really are.

What really happened during Cupcakes. Not quite as gruesome as what everypony assumed.

This story is a sequel to The Horrible Misunderstanding of Cupcakes

Pinkie Pie tries to tell her friends the true nature of the events they witnessed earlier. This might be a little harder than expected.

Tragedy strikes the Pie Family, scarring Pinkie through her childhood and for life. As Pinkie comes to terms with her apparent former Gypsy roots, her out witting mind gets the best of her and she is convinced that something can be done. Even if it means using those around her. Especially her innocent little helper, Apple Bloom.

Pinkie Pie didn't tell a lie about her past, she just didn't tell them what it really meant either. In this short story, Pinkie Pie's past is brought to light, all because a very curious mare was confused as to what the town party pony really meant. Twilight's need to learn has unearthed something that no pony could have ever come to expect about a certain Pink mare...

(Click image for better look at Pinkie's Scars)

Twilight Sparkle caught and sent Pinkie Pie to the Ponyville Mental Hospital in hopes of bringing her party friend back, despite what other ponies say to her. On court day, she planned on getting her now stable friend out, but the said friend says otherwise.

An Unofficial 'sequel' to Cupcakes. A quick One-shot I thought up and wrote out of boredom. Now flood the comment's section with whatever you like to say, I need feedback! I need the stuff! (I don't really abuse drugs... just to let you know.)

Non-MLP-related-fanfictional story is right here. It's a little longer, different cast of characters but pretty much the same story.

"Haunted by the Past"

The Spirit Pony is responsible for the End of All That Ever Was. It has always been so. This particular End looks like being a straightforward one – until a certain pink pony intervenes to prevent it happening. Pinkie has a very, very good reason for stopping the Spirit, too...

Now has a reading by... er... me! And another one by hystericaldominolego!
22/11/19: New! Dramatic reading by Scribbler, featuring Quirky Craft and Illya Leonov!

Featured by Equestria Daily
Featured by the Royal Canterlot Library
Featured by Seattle's Angels
"a look into the power of Pinkie ... Highly Recommended" -- PresentPerfect
"a delightful sense of unreality to the whole thing ... 9/10" -- Soge