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

Discord still has a lot to learn about friendship. Spending some one-on-one time with each of his new friends is helping. If only they wouldn’t get so upset about being turned into fruit or having their hair eaten.

What’s that? Make my life a living nightmare? Foolish pink pony! I’m Discord, the Lord of Chaos. What could a simple pony like you possibly do to me?

Inspired by the art of the ever so talented Madacon and a conversation with the stories editor Tired Old Man.

Rainbow Dash has always been full of herself and always thinking that she was the coolest mare in Equestria. She had always suspected that all the mares were into her, jokingly. Then one day it suddenly started coming true...

When Spike tries to get help from Celestia he only sets off a chain of events that will forever change Equestria.

(Featured 7/22/14 filtered view only though)
(What? This actually got in the feature box without any filters on 7/23/14 Thanks for all the support guys.)
(Sex tag because of the nature of the dialogue and because reasons)
Art by PolyCysticOvary from deviant art. Used with Permission.

Twilight, seeing that her friend needed a little bit of companionship, decided to help him get a date.

But boy, did he aim a little too high for her taste.

Now, her and Spike need to help this putz of a human snatch a date from one of the most undateable beings on the planet, Princess Celestia.

Needless to say, they're doomed.

Cover art used with permission by Lydia-Rawr

Warning: Story will contain horrible romance clichés, cutsieness, and all around silliness.

You have been warned.

The Dragonborn, a legendary warrior capable of absorbing a slain Dragon's soul, and knowledge, directly, forever killing it. The Last Dragonborn had defeated the first, stopped the plans of a Vampire cult, and built his own lakeside home, before finally slaying Alduin the World Eater and fulfilling his fate. Now, after all the challenges he has faced, the Dragonborn is sent to a realm where Friendship is Magic, and there is no mead. Finally, to cap things off, he kind of... well...
Became a Dragon.

Applejack, Twilight, and Rainbow Dash really enjoy each other's company. So much so that some ponies are beginning to wonder about them. Twilight and Applejack are a couple after all, so its a bit unusual that Rainbow always seems to be invited along. But sometimes, a couple is more than two.

Thanks to Steel Resolve, Lycan_01 and Macdjord for editing and brainstorming!
Cover art by Graystripe64.

This story is a sequel to Friday Night Twilight

A cartoon pony named Twilight Sparkle visits me every other Friday night. We talk more than we used to, but she still makes me watch that show of hers. Isn’t anything ever going to change?

Chinese Translation by ComradeSpark

Note: that Romance tag doesn't equate to mushy stuff, and it's not the reason for the Teen rating. This is much closer to Everyone than Mature.
Cover art generously provided once again by statoose
Big, heartfelt thanks to Skeeter The Lurker for helping me deal with reader reactions, and to Craine for proofreading the new final chapter.