Sunset Shimmer Vs. Sunset Shimmer is the 15th episode of the first season of Thomas' Adventures Chronicles.
Sunset Shimmer been having the same nightmare over and over again about the time at the Fall Former where she was once a mean student and turned into a demon to destroy Twilight and her friends.
Sunset Shimmer decided to visit Twilight at her Rainbow Kingdom and explain about the same nightmare she's been having and claimed that she's might still had her bad side somewhere. Sunset Shimmer then ask Twilight to cast a spell to expel the negative parts of her personality, but accidentally creates an evil reflection of Sunset Shimmer in the mirror. The evil Sunset Shimmer escapes the mirror and runs off to the Dieselworks.
At first Diesel 10 didn't trust her. But she reveals that she is an evil side split from the good Sunset Shimmer which she gave Diesel 10 an idea. Meanwhile Twilight and the good Sunset Shimmer told Thomas and the others what have happened. They were shocked when they learned that Sunset Shimmer had split into two. Princess Cadance explain that they should never have used that spell in the first place. Otherwise the bad Sunset Shimmer will do anything to get rid of the good Sunset Shimmer.
Meanwhile the bad Sunset Shimmer along with Lord Rothbart and the Grand Duke of Owls startec to take action to capture all the steam engines and take them to the scrapyard to make way for the diesels. They shrinks and imprisons James, Edward, Emily, Duck, Oliver, Gordon and Henry to start off with and went on their way to the smelters. Thomas, Twilight, Percy, Pinkie Pie, Applejack, Rainbow Dash, Fluttershy, Rarity, The good Sunset Shimmer, Annoying Orange and his friends follow them and manage to rescue the their friends just in time.
While the good Sunset Shimmer battles the bad Sunset Shimmer, Thomas, Twilight and the others battles Rothbart and the Grand Duke of Owls. Rothbart turned in the Great Animal and battled against Twilight and Cadance, Thomas uses his lamp to blind the Grand Duke of Owls far away. Twilgiht and Cadance soon manage to defeat Rothbart. Soon the bad Sunset Shimmer was defeated. Quick as a winck, Twilight her reversing spell to put the good and the bad Sunset Shimmer back together.
With the battle over, Sunset Shimmer felt very guilty about what she had done and felt like she don't deserve to be everyone's friend anymore. But Thomas and Twilight remined her that they are still her friends no matter what will happend to her, they will always be at her side if it happens again which cheered he up.
Back home, Sunset Shimmer never had the same nightmare ever again instead she dreampt about being with her friends and always be the good Sunset Shimmer.
- Thomas, Princess Twilight Sparkle, James, Gordon, Henry, Emily, Edward, Duck, Oliver, Percy, Pinkie Pie, Rarity, Rainbow Dash, Applejack, Fluttershy, Princess Cadance, Shining Armor, Sunset Shimmer, Annoying Orange, Pear, Apple, Passion Fruit, Midget Apple, Marshmallow, Grapefruit, Grandpa Lemon, Nerville, Diesel 10, Rothbart and The Grand Duke of Owls are starring in this episode.
- Scenes from Thomas' Adventures of My Little Pony: Equestria Girls will be used as Sunset Shimmer's nightmare.
- This episode is based on Disney's The Wizard Return: Alex vs. Alex.