Greetings From Unicornia

Greetings from Unicornia is an animated short included with the US version "The Runaway Rainbow" DVD.

Story
Rainbow Dash is away in Unicornia, the home of unicorn ponies and has sent a post card that Puzzlemint receives, explaining details of her adventures there. With Pinkie Pie reading it to others, Rainbow Dash is given a tour of Crystal Rainbow Castle and finds a room filled with rubber balls. Eventually, she and Rarity decide to hop on one and end up outside, leading to a song that explains how rainbows are made and more. Rainbow Dash returns by the time the rest of the postcard is read and brings a rainbow along with her.