The True Purpose of Doraemon's Mission: The overarching premise reveals that Sewashi didn't send Doraemon merely to make Nobita rich, but to fundamentally transform Nobita’s character. In the original unaltered timeline, Nobita fails exams, sets fire to his own business, goes bankrupt, and marries Gian's sister, Jaiko. Doraemon’s presence alters the timeline so that Nobita marries Shizuka, creating a stable, loving family tree.
The "Lie 800" Miracle: When Doraemon is forced to return to the 22nd century forever in the Goodbye, Doraemon arc, he leaves Nobita the "Lie 800" potion, which turns spoken statements into falsehoods. When a grieving Nobita cries that Doraemon will never return, the gadget renders it a lie, instantly bringing Doraemon back for a permanent reunion.
The Maturity Paradox: The major underlying twist is that Nobita’s eventual adult success comes not from using Doraemon’s gadgets, but from learning to live without them. Adult Nobita declines to see Doraemon when visiting the past, recognizing that Doraemon belongs to his childhood and that he must walk his adult path on his own strength.