Erika to Satoru no Yume Bouken (1988)

Erika to Satoru no Yume Bouken is a 1988 Japan-exclusive adventure video game for the Famicom. It is a fairytale-inspired menu-driven adventure game. Players use the menu commands to interact with the world: moving around, looking around, picking up objects, talking to people, etc. The setting of this game is 20th century Japan. In a novel twist, the two characters of Erika and Satoru (who are depicted as twin schoolchildren) are independently playable - either a single player switches between the two, or a second player takes over the second twin. Both characters need to be in the same region to converse with NPCs, but are otherwise free to explore the map autonomously. Two-player adventure games are very rare; even in Japan. However, only one person can partake in the animal quiz portion. Failing the quiz will force the player(s) to start from the beginning. An odd bit of infamy related to this game is a secret developer's message that can be found if the player inputs a list of button presses after waiting some time after the game ends. Inside of which is a litany of compliments and complaints to other co-workers, including some sexual insults which are deeply at odds with the child-friendly nature of the game. It also refers to, among other things, the work Atlus did for LJN including The Karate Kid.