Professor Layton and the Miracle Mask (Nintendo 3DS)
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Hidden Door Secret Episode 1
In the game's Top Secret menu, there is a section called The Hidden Door. One of its options can only be unlocked by using a 3DS system-unique password found in the Hidden Door section of Professor Layton and the Last Specter. It gives you access to a bonus conversation between the cast, as well as a brief quiz about what happened in the previous game.
Hidden Door Secret Episode 2
In the game's Top Secret menu, there is a section called The Hidden Door. One of its options can only be unlocked by using a 3DS system-unique password found in the Hidden Door section of Professor Layton and the Azran Legacy. It gives you access to a bonus conversation between the cast, and foreshadows events in the Azran Legacy.