My Teacher
S1:E38
1979
IMDb
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.