Octavia not only fearing for what's to come of her sister Pinkie Pie, and Bellamena, she also learns that the Mayor and his colleagues are a part of a foundation that is teeming with aggressive energy that can cause elaborate nightmarish pattern, that jitters their brain waves.

Could this be the source of Pinkie's repeating nightmares? You will find out as the spoilers remain in the respective paragraphs.

Pinkie Pie is being tormented by horrific nightmares. Unable to deal with it by herself anymore she seeks out Twilight's help, but will it have been the best decision when she finds herself alone in an abandoned, fog filled Ponyville?

Sequel: http://www.fimfiction.net/story/4676/Too-Shy-for-a-Rainbow

There have been a LOT of high-quality readings of Silent Ponyville, but this one is my personal favorite:
https://www.youtube.com/playlist?list=PLGh01rbB4o3xoSV7a6Omc-UJROXHRZ1Hv

Ponyville is visited by a mysterious mare that seems to have lost all happiness in her life, but there's more to her than what's on the outside. She has forgotten who she is and goes by the alias of Silent Fear. The Mane 6 takes it upon themselves to discover the truth about her.
Fears are unleashed and tears are shed as Silent Fear's memories are rediscovered.

A (kinda) crossover with Silent Hill

When Lance Strongshy's medical career is endangered due to relentless nightmares depriving him of sleep, his daughter Fluttershy once again overlooks the horrible past she suffered at his hooves and enlists the help of her friends to cure him. But, when the only sufficiently expedient solution turns out to be a certain spell that Twilight was instructed to never cast again, it becomes uncertain if their efforts will save him, or utterly destroy him.

A sequel to JakeHeritagu's Silent Ponyville 2, read that first if you haven't already: http://www.fimfiction.net/story/4868/Silent-Ponyville-2

And THAT one is the sequel to JakeHeritagu's Silent Ponyville so if you haven't read either here's where you should start: http://www.fimfiction.net/story/106/Silent-Ponyville

(First cover art by http://manwhomurderedtime.deviantart.com/ )
(Current cover art by http://www.fimfiction.net/user/SamRose )

Octavia returns to her apartment complex after having finished her concert tour with her band. She heads up to her small apartment looking forward to a comfortable night of rest and relaxation in her home.

Part of an Art Trade I had with Star Sage.
Warning: Involves unaware vore.

In her search of new methods to increase her speed, Rainbow Dash came up with the idea of using a magic stone she got from Zecora. Although it's a bit unorthodox, she can already see the improvement. That is, until something unexpected happens involving a certain farmer.

This is a collection of short, fun Nightmare Night themed stories
Nightmare Night -- It was only a bad dream, right?
Theme Party -- It looked like nopony was going to come to his theme party, not after last year's Police bungle! His party was saved by some late comers.
The Sweet Spot -- Leroi made a bit of a mistake when he tried to threaten the owner of the Sweet Spot to get goodies.
Nightmare Vision -- Was the Nightmare Night chant from the graveyard a prank?
Putting the Bite on Trottingham -- Prilla was not having a happy Nightmare Night until she stopped by the Sweet Spot and accidentally made a wish.
Nightmare Night at Grumpy's Cave -- A Rom mare comes to Gumpy to get her sister healed. The Ponyville Council has closed down all Nightmare Night parties to boost their Charity gala. Grumpy invites the Rom to his cave for NN and the party snowballs!
Nightmare Night Surprise! -- Unger was "digging up the past" when the past caught up to him!
The Tail of the Ghost -- Master Sargent (Ret.) of the Royal Armored Pegassi and the Royal Road Fast Post is given the Royalmont Chateau by their Highnesses. The Equsetrian National Bank finds that it is unwise to mess with a Royal Gift -- that happens to be haunted.
VIGNETTE AT A HAUNTED MANSION PARTY -- Nemmie goes to spend Nightmare Night in the haunted ruin of Crawfeather.
THE EMPTY GRAVE -- It is unwise to betray a real witch.
GNAWED EVEN -- Even monsters have natural enemies.
CRACKING THE CODE -- What could possibly go wrong with cracking an ancient code in a graveyard – on Nightmare Night?
REPOSSESSED -- What happens when a being of the Underworld tries to collect the soul of Sawnax?
NIGHTMARE BLESSING -- Penny looks like a “fake witch” pony to Red.  He jumps to the wrong conclusion.
DEAD EASY -- Ferd made two mistakes on Nightmare Night.  First was trying to rob the Sweet Spot.  The second was making a wish …
BONNIE BONES -- A young unicorn filly was abandoned in the cemetery because of a stunted horn.  She was raised by some who are no longer ponies.  She gets taken to Miss Cherrilee’s school by the truant officer.
CRAGENMARE -- What reason could there be for a Nightmare Night party for foals in the ruin of ancient CRAGENMARE, far outside of Ponyville?
LUNA’S NIGHTMARE NIGHT -- How does Princess Luna spend a night that really is ALL ABOUT HER?
SQUEAK’S NIGHTMARE NIGHT -- Squeak, a preternaturally long lived thestral, who helped Caramel Treat’s shop on her first Nightmare Night Celebration, drops in to see his friend on another Nightmare Night after some years have passed.
BEHIND YOU! -- Cortwrong makes the mistake of stealing Sarrie’s manuscript.  He looks where he should not have.
THE LUCK OF BLACK CATS -- Black cats may bring bad luck, especially if you are doing bad things!
NIGHTMARE NIGHT AT THE SWEET SPOT -- Roe, the magical wish granting deer in disguise, throws a Nightmare Night party for his pony family and some friends.
BLOOD RED ROSE -- Pointea makes a spell to draw some company for Nightmare Night.  Did she get the spell done right?
NIGHTMARE NIGHT LESSON -- Luna accepts an invitation from Caramel Treat and Fangrin to preside over their Nightmare Night celebration as the Nightmare. She teaches both an unruly Count and a young filly just who is REALLY important to Equestria.
A QUIET EVENING -- The CMC enter the Ponyville Cemetery with the goal of setting spring "ghosts" to frighten off some vandals. They have some help from Bonnie Bones and a few others that they did not expect.
NO REFUND A meeting in the Ponyville Graveyard reveals that it is unwise to try cheating either Death or Grumpy Goat!
CRAWFEATHER! -- Just outside of Ponyville lurks the haunted mansion of Crawfeather TRIGGER WARNING: Multiple murders by ax, poison and stabbing. You have to get those ghosts in there somehow, right?
POSSESSION -- This tale is set in Sawnax’s youth. It is a prequel to REPOSSESSED. Sawnax is a rotten colt, who blames others for the results of his own actions. Claficus, a demon, offers him a chance at revenge. It does not go quite as he hoped that it would.
A BONNIE DAY -- Bonnie Bones is out in daylight though the Nightmare moon shares the sky with her sister. Morgripe and his buddies come to vandalize the graveyard in daylight just before Nightmare Night, thinking to avoid blame by being out and about with witnesses on the night.
BONNIE BONES’ ERRAND -- It is the day before Nightmare Night and Bonnie is out shopping! She has a bit of a run in with Morgripe’s old graveyard vandalism accomplices but gets what she was after. She goes to a Nightmare Night party later.
THE MORGRIPE REPORT -- Bonnie Bones is interviewed by a reporter from Ponyville’s Dark Secrets magazine about the disappearance of Morgripe.
INVITATION TO A FEAST -- It is the night before Nightmare Night. Melissa, the reporter, true to her word, brings her story to Bonnie Bones for approval. She discovers some things about Bonnie and is invited to share in a Nightmare Night with Bonnie in the Borderlands of Nightmare.

It's Halloween and Sunset Shimmer and the others are looking forward to having a good time. However, when Twilight offers to make their costumes look more realistic, they get more than they bargain for when they actually transform into their costumes! Now, Sunset is the most brilliant unicorn wizard in existence, Rarity and Applejack have switched perspectives, Pinkie has become psychotic (in a bad way), Fluttershy and Rainbow Dash are sporting fangs and fur, and Twilight must keep her alter-ego from reasserting itself! Can Sunset and Twilight reverse the spell before midnight when the spell becomes permanent and they all remain trapped in their altered forms forever?

My entry in the FlutterDash Contest: Nightmare Night, What A Fright!

Now has a TVTropes page.

A mysterious spell causes the mane six to slowly transform into monsters at night. Can they find a way to undo it before it becomes permanent?

A young colt who works at Sweet Apple Acres tells his mom about his day, and then says goodnight like he does every night.
A heartwarming tale for Nightmare Night or Halloween (if you are human)