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

Amethyst and Steven were just enjoying a sunny afternoon outside the Big Donut in Beach City. Never in a million years though would they have expected to find a young...something...in a dumpster. Now seeing that this creature has nowhere to go, the gems decide to take it in and maybe try to find out what the deal is with the little monster's bad case of amnesia, and all the while dealing with the child's extraordinary powers.

Frankly, a child Discord may end up being more trouble than he's worth for the Crystal Gems.

An MLP/Steven Universe Crossover

"Sunset, you weren't the first unearthly threat to come to this world, and you won't be the last. If we seem calm in the face of strange events, it's not because we're oblivious or indifferent to them. It's because they're not strange to us. The Fall Formal may have been the most important night of your life, but to us... it was Thursday."

(Slice-of-life adventures of Canterlot High's unlikely band of monster hunters.)

Now with a Tropes page, courtesy of AnoneMouseJr.

This story is a sequel to Princess Celestia's Newest Arch Enemy

After successfully defeating both Princess Celestia and Luna on his first day as super villain, the colt known as Bad Dude sets his sights on much larger projects. Namely, the creation of Equestria's first ever super villain group known as The Coalition of United Terrible Evils. Or C.U.T.E. for short.

But were villains ever truly meant to play nice with one another?

Artwork by Shadow Bolt.

More Bad Dude art by TurnWrongattheFork. HERE!

A mother will do a lot for her child, even give them up if it meant them having a safer life growing up, despite the obvious pain that comes for the parent.

That pain is something Queen Chrysalis has gone through for eighteen years, but now the time is upon them, and she wants her daughter back. Even if that means invading Canterlot during a royal wedding.

Edited by RC2101_Copey
New cover art was created by the talented Jesuka
Now has a TVtropes page: http://tvtropes.org/pmwiki/pmwiki.php/Fanfic/Change
Go watch the reading by Skijaramaz: https://www.youtube.com/watch?v=Ecqtu_Djrw4

(Featured on 18/10/2015, the first day! Thank you!)

Change is now a printed book, information here: https://www.fimfiction.net/blog/732008/i-got-a-thing-change-is-now-a-physical-book