Soon before nightmare night. Applejack was preparing herself a cow costume. Rarity on her side still hadn’t decided what she would disguise as and decided it would be a good idea to go ask Applejack.
 
Applejack showed her her costume and Rarity liked the idea but she would have to rework her costume entirely, this cow costume would simply not cut it. The quality was really not there. They both got the idea to costume as joined cows so Rarity was going to make a costume that both can enter.
 
Applejack on her side got a better idea then Rarity’s and it was to go ask Twilight for help, with her magic, she sure can do something really realistic.
 
They went to Twilight who accepted to help them. The spell was simple. It would turn them into cows and also join them together randomly for a whole day. Both were ready for this. Twilight cast the spell on them. they turned into cow ponies that were joined together by their udders.
 
Rarity and Applejack blushed and felt a bit uncomfortable about it. Twilight told them to relax and that she didn’t choose how they would be joined, the spell did. She also said that this was just a practice and so that she would turn them back since its not Nightmare Night. But she she tried to undo the spell, it failed.
 
Twilight couldn’t turn them back, the spell was permanent. Both Rarity and Applejack freaked out and since then they live together as cow that share the same udders.