Yu-Gi-Oh! Duel Monsters

Evil Spirit of the Ring (1x13)

:

Yugi's classmate Bakura, possessed by his Millennium Ring's dark powers, traps Yugi and his friends in a Shadow Game where they become the cards themselves. Not only must Yugi battle to avoid becoming a permanent part of the card game, but also free Bakura's soul from the Millennium Ring's control.