The Mad King in Equestria

Ryan Haywood of Achievement Hunter/Rooster Teeth was walking through the empty RoosterTeeth building after the LetsPlays for that day had been filmed and the rest of the AH crew had left but Ryan had made it his sole job to make sure that all of the technology was working correctly before he left. As he roamed the hallways and checked the computers Ryan thought to himself "I wonder what kind of tortures I can plan for the next King LetsPlay?" for the man was known as the Mad King for a reason and the main reason was probably is animal army in his house but one animal in particular the one that started it all, a cow named Edgar. Edgar is probably the whole definition of the Mad Kind as Edgar is a cow who lives in a hole beneath Ryan's house in attachment to Edgar's hole though is the biggest part of his second reign a dungeon where Edgar was killed but not the real Edgar it was a human doppelganger  named Kerry but after Kerry's defeat at the hands of Gavin Free Ryan gave up his Kingship to Gavin who quickly lost it to Ryan once again. So as Ryan wondered the halls of RoosterTeeth he had plenty in mind soon he came to the room which held his crown so jokingly he put it on to wear until he finished checking the technology and shutting everything down. Soon he reached the last computer his computer but something strange was happening with it "why is it emitting a rainbow glow?" he thought. So he walked up to the computer to check the wires which all were fine so he just decided to manually shut the computer down but as soon as he touched the computer there was a blinding rainbow colored flash and Ryan was gone crown and all.

A few minutes Earlier in Twilights Library

"Come one Twilight! What's taking so long?" Groaned Rainbow Dash as she had been waiting for the last hour for Twilight I show her this new spell

in response Twilight replies "I'm sorry Rainbow but I have to make sure everything is correct for this spell to work and even so I have to prepare backup spells in case something goes wrong."

letting out a sigh Rainbow Dash Says "Fine."

to which Applejack replies "Ah come on Dash she'll have the spell ready in no time just you see."

Rainbow Dash replies with "I know but how long will it take?"

causing Twilight to reply with "Don't worry Dashie I'm about done and I have backup spells for any problem that may arise so don't worry."

then Rarity replies with a slight accent "Oh but darling don't rush yourself to hard it may mess up your mane."

"Rarity I know you're a fashionista and all but can't you think about the spell it could be absolutely amazing so amazing actually that we need to throw a party because of the pure amazingness of it!" says Pinkie Pie in a happy voice thinking about all of the different possibly fun outcomes of the spell

"Or it could be a scary outcome." replies the quiet and absolutely cute voice of Fluttershy

which Applejack replies with a calming tone "Don't worry there's nothing to be afraid of especially with Twilight on the Job, besides the only scary well not really scary but strange thing thats been happening around Ponyville for me is that the cows have been acting strange lately."

then Fluttershy looking up says to Applejack "Maybe I can check on your cows later to see why they are acting strangely."

Applejack responds with "Of course you can Fluttershy

" then Twilight announces "OK the spell is ready-

then being cut off by Rainbow Dash Yelling "It's about time can we just get this over over with I've waited long enough!"

Twilight just sighs and says "OK fine." she then casts the spell causing a blinding rainbow colored flash.

Meanwhile on Ryan's end after he touched the monitor he felt a strange sensation throughout his body as he started turning into a unicorn. The mane six watched in awe as the rainbow flash enveloped the room then suddenly it stops and out of the flash flies a golden crown which causes Twilight to look confused and say "Well that wasn't what I expected." Rainbow Dash was about to reply when she is cut off by another blinding flash and once the light dies down a light brown unicorn stallion with a brown mane and a cow with a crown cutie mark is revealed in the center of the room.  Upon seeing this stallion Twilight asked her friends to him to make sure that everything in the library was ok, then she walked over to check the stallion to see if he was ok and then was relieved seeing that he was fine then upon seeing his cutie mark of a cow and a crown she realized that the crown that first flew through the portal belonged to this stallion so picking it up she brought it to him and put him onto a bed with the crown resting on the nightstand though she wanted to know more about how the stallion got here she knew it would have to wait until he woke up.

Twilight then asked all of her friends if everything in the library was ok and upon confirmation of that she asked them to leave while she figured out what to do about this strange stallion and promised that they'd talk about it tomorrow. Once her friends left Twilight called Spike so she could write a letter to Celestia telling her what happened because if anypony would know what to do about this strange stallion it would be Celestia.