Big Mac and Applejack have switch bodies, but why and how?

The main six gain powers after Discord is released somehow, after Discord is gone, they find King Sombra released Discord so they find a defeat King Sombra

Rainbow spend Hearth's warming Eve with her marefirend Applejack only to have a mysterious present appear under the tree.

Fluttershy wakes up one day to find that she is married to Rainbow Dash, she also has a daughter and a son, Fluttershy finds out what happened, and things go back to normal the next day, but she had changed

Fluttershy has been emotionally broken by her ex-coltfirend and her friends want to get her back to normal, by fixing each problem one by one. Rainbow Dash also decides to tell Fluttershy about her feeling for her.

Twilight and Applejack both love Rainbow Dash, but only one of them can have her. Twilight and Applejack do everything they can to make Rainbow chose one of the other.

Rarity decides to rest after working on new dresses, but she realizes she worked so hard she forgot about her weekly spa trip with Fluttershy, but Rarity has had a crush on Fluttershy four a while after the spa trip Rarity confesses her feelings.