Yu-Gi-Oh! Capsule Monsters is a twelve-episode mini-series commissioned, produced, and edited by 4Kids Entertainment (much like Yu-Gi-Oh! The Movie - Pyramid of Light) that is a part of the Yu-Gi-Oh! franchise.


Set before the end of the second Yu-Gi-Oh! anime series (Yu-Gi-Oh: Duel Monsters) - between the Grand Championship and Memory World, Capsule Monsters involves Yugi, Joey (Jonouchi), Téa (Anzu), Tristan (Honda), and Yugi's grandfather Solomon (Sugoroku) being pulled into a world where Duel Monsters are real. They find monster capsules that they can use to summon monsters. However, in this strange new world, they battle monsters and when their monsters are attacked they feel the pain. Atem believes it to be some sort of twisted Shadow Game.

Source: Wikipedia