MLP/Undertale crossover.
Not a PWNY-verse story.

Long ago, the Monsters and Humans fought a great war. The Monsters lost, and were sealed in the Underground. It would take the power of seven human souls to break the barrier that kept them imprisoned. They only had six. And so the Monsters waited and hoped, praying that another human would find their way to the Underground. Some thought the seventh soul would give their King the strength to break the barrier. Some dreamed of a human who would be their friend, and save them all...or had nightmares of one who would bring back the war.

...but nobody came.

...but somepony did.

Eons after the war, with no way to tell how much time had passed above, a tiny blue filly with wings and horn fell into the underground, calling for her Mama. None knew the poor creature's nature or origins...but her soul was powerful with magic, even more so than a human soul.

None can know what will come...of this little 'Woona'.

Cover art by Sanyo21

While going out for a drive, a young woman named Cassy becomes inexplicably lost in a strange new world beyond her imagining. The fact that she has also somehow been unwillingly turned into a weird spider monster is not helping either, especially as far as a few of the locals are concerned.
And she only has so many cigarettes.

This story is a comment-driven tale, wherein the events that take place throughout are decided by the readers themselves.
Conflicting tags: Adventure/Slice of Life. Potentially many others, but that remains to be seen as of now.
T rating for some tobacco use, particularly early on, though I don't necessarily endorse it.
Cover art by yours truly.
Also it is a Displaced

Apple Bloom was just helping her sister at a local farmer's market when she met the most unusual employee at a stand. What follows is a filly getting the most unusual and depressing advice she's ever received.

This is a MLPXUndertale crossover. May contain minor spoilers to Undertale.

Derpy was on her regular mail route when a sudden crash caused her to meet the most peculiar creature. A little creature called Temmie. Now, she finds herself promising to help the little guy get home. Little does she know, the creature has a charm that will make anypony want to befriend the lovable little guy.

This is a MLPXUndertale crossover. May contain minor spoilers to Undertale.

I would like to thank Brony Dragon for the cover art!

Featured on Fimfiction's main page on 1/24/2016!

They say there's a judge in Equestria with the special talent of discerning intent. He has a near spotless track record and the support of the Crown. This is a day in the life of said judge.

there are shockingly few good undertale/mlp stories. like, you'd think there'd be more because of how popular both things are, but no.

Update 4/12: So I just found out someone did a reading of my story. Go check it out Here!

Convinced she'll never find peace after the Anon-a-Miss incident, Sunset Shimmer decides to leave Canterlot High for good. When her friends go after her, they wind up getting lost and falling underground. And when Sunset falls in after them, she's left with a choice.

Escape to the surface and keep her sanity or risk losing herself in the darkness.

Crossover with Undertale. Comission from calinjc

They fell from the sky, only to have their landing broken by flowers carefully tended to by a crystal pony. The pony was scared away. They were scared stiff, but there was no running. The pony world they found themselves in was very real. Their choices would count against them...

I will try to keep it interesting and amusing. Think I did a good or bad job? Let me know! I love comments, loving or scathing, just speak.

Once upon a time a person died living a good life, when they died they were was given a second chance but didn't want it. Too bad they didn't have a choice in that matter but at the last moment they used their second chance to bring me back.

I am Chara Dreemurr, Princess of the Underground, Wife of Frisk Aster, and I will fix the mistakes of the past. I will protect my Family and bring back the Monsters, even is the price for such a thing is my corrupted and blackened soul.

Descriptions edited 9/16/2019 to better suit the story.
Tags will be added or removed as necessary.
Story Cover Image changes to reflect the state of the story so expect it to change often.

Story Featured 10/15/2019

Sans should be dead, he only has one HP after all, he felt the knife hit him, he saw himself turning to dust. Then why is he not dead?

An Undertale and My Little Pony crossover. Of which I own neither, Toby Fox owns Undertale and My Little Pony belongs to Hasbro. Please enjoy
Featured on 4/8/2017, 5/5/2017, 4/16/2018. 10/8/2018 Also on popular stories! Thank you so much!
100 likes! Thank you!! 200?!?!? 5/14/2017 OMG! Thank you!!! Featured August 27 2017. :D

New coverart provided by Supersheep64. Everyone, please give them a huge round of applause!

With the barrier broken and the Monsters free, Asriel Dreemurr is apprehensive about what he knows is coming. He won't be able to maintain his form for much longer, and is afraid of no longer being himself again.

Then, a mysterious figure offers him a deal. A second chance, an oppurtunity to redeem himself... but the figure chooses where he gets that second chance.

Not wishing to become a Flower again, Asriel takes the chance, and is transported to a whole new world of magic, wonder, sights no Monster has seen, and of course, the magic of harmony and friendship.

And into whose hooves does the figure send him the young Prince to? Why, the hooves of someone else who has been given a second chance, and seeks to redeem herself and make up for the mistakes of the past. None other than the Princess of the NIght, Luna herself.

Come along as the young Boss Monster does his utmost to make good use of this second chance, and along the way, find family in a land far from his own.

Awesome cover by Cyaneworks over on Furaffinity~!

Has a companion story right here, Hopes and Dreams at Canterlot High

EDIT: (Featured *numerous times, seemingly now after each update lol*)
Thank you thank you thank you aahhhhhh you're all amazing