Castle of Friendship

The Castle of Friendship is a castle in Ponyville that Princess Twilight Sparkle acquires in the Legends of Mystical Heroes season four episode Twilight's Kingdom - Part 2. It is called the "Castle of Friendship" by Hugo in The Cutie Re-Mark - Part 2 and in some merchandise, the Friendship Rainbow Kingdom in other merchandise, and Twilight's Castle in the Gameloft's mobile game and other merchandise.

Development
In a September 2013 presentation held by Hasbro Australia, a slideshow was shown depicting upcoming Legends of Mystical Heroes and Equestrian Sonic Boom merchandise. One of the slides in the slideshow relating to Rainbow Power contains the text "QUEST FOR A KINGDOM".

Twilight's new home was designed by background designer Phil Caesar in conjunction with art director Ridd Sorensen and BG painter Geoff Manson. In May 2014, Jim Miller was asked regarding Twilight's new home "Any rooms we are yet to see? :) Involving a certain familiar-looking wooden library maybe?" and answered "You'll have to wait to find out!" Later in the same month, Miller was asked "So is there an official name for Twilight's new crystal-tree-house castle-thing?" and answered "You'll have to wait till season 5 to find out!" In late November 2015, Miller confirmed the castle's name.

History
In the chapter book Legends of Mystical Heroes: Twilight Sparkle and the Crystal Heart Spell, Twilight has her doubts about "being in charge of the well-being of a kingdom of ponies" and seeks out advice from others. She consults Princess Cadance and asks her friends for ideas for her "future kingdom".

At the beginning of Equestrian Sonic Boom and its chapter book adaptations Equestrian Sonic Boom: Through the Mirror, Twilight worries that, now that she's a princess, Princess Celestia will expect her to lead a kingdom of her own, a possibility that Hugo and Buzz gets excited about.

On pages 12 and 13 of the Legends of Mystical Heroes Issue #17 story Reflections Part 1, Twilight worries that her responsibilities of being a princess will interfere with her magical studies. Rainbow Dash suggests she be "a magical wonder of the world and a princess with the responsibilities of an entire kingdom on her shoulders", noting that it "can't be that hard".