Anime-only
There are many cards seen in the anime that have not been created for the real game yet. Some of them, such as "Cursed Twin Dolls" and "Dark Sanctuary", are quite hard to create a real ruling for in the real game (the latter card might even require the use of paper and a writing utensil so the player can write down which monster to "possess"), so they may never be released.
Also, some cards do exist in the TCG/OCG but have different effects in the anime; these differences can range from changing an Anime Dark Synchro Monster to a Synchro Monster (i.e. "Hundred-Eyes Dragon") that have different effects completely, or something like "Destiny HERO - Dreadmaster" that can use its effect whether it was summoned with "Clock Tower Prison" or not. For many cards from the manga though, their effects have been specified to support a specific element of the game, like Archetypes or Attributes.
