Doraemon (1979)

I'll Be My Own Teacher (1x45)

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Nobita's parents decide to get him a tutor as his grades are bad so Nobita decides to use himself 3 years in the future to answer his school questions now. But his future self is dumb because Nobita did not study and that Nobita too has a future self who turns up and complains that he is dumb too because Nobita 3 years in the future did not study either. The three of them go to the kindergarten Nobita, saying that if they want to improve their grades,they have to start from the beginning. However none of them has the heart to tell the kindergarten Nobita to study, so they return to the present time.