Twilight was testing out these mirrors to travel to different dimensions. However, an unknown error of Twilight's magic caused her to enter a special world called the Imagisphere. The Mane 5, CMC, and Spike joined in as they traveled through the mirror portal, which is how they got there.

They traveled into a mystical place called the Imagisphere as it's made up of creative thoughts and ideas anyone ever had. They all come together to form a planet called Craftworld. As the Group meets Sackboy in his home planet and his village called Loom, Vex without any reason captured Sackboy's friends and plotted to turn Craftworld into a world full of Nightmares and Chaos with his Topsy Turver. It's up to Sackboy, Spike, and the CMC to stop Vex from rising the Uproar into this peaceful planet and saving the Mane 6 from his nightmarish goals.

A crossover between MLP and Sackboy: A Big Adventure

MLP is owned by Hasbro

Sackboy is owned by Sony/Playstation