There is still a question about Nobita's time-space transmission of cats and dogs.

Because Daxiong sent them 300 million years ago, there was a cat and dog country. This is a causal relationship, which proves that the history of Daxiong's life is the existence history of the cat and dog country. However, in the time tunnel, Nobita and his men took cats and dogs to the time tunnel to reach 300 million years ago, and did not encounter time distortion, because the cat and dog country did not exist at that time. However, around 300 million years after sending cats and dogs, Nobita and his men did not encounter time distortion when they came back, because the country of cats and dogs had not yet been built. However, when Daxiong went to the cat and dog country the next day, the cat and dog country was already born, and the old man sat down and invented the time machine. So Ah Yi couldn't go to the future, only went to the country of cats and dogs after 1000 years (actually needed by the plot), and when Daxiong visited Ah Yi, the country of cats and dogs, he also encountered the distortion of time and space, which proved that the time and space of the country of cats and dogs covered the time and space of the country without cats and dogs, so it was distorted. Of course, after the residents of the country of cats and dogs immigrated, a new history came into being, so Nobita finally returned to 26544.

It was inevitable that Daxiong came to 300 million years ago with cats and dogs, so the future was ignored. Although Nobita didn't know it, what Nobita did was just to conform to history. Daxiong has changed history many times, but the main line history has not changed. In other words, this irrelevant history changed by Nobita will not have any influence on the future of the main line, so the patrol of time and space will be ignored.

In fact, the time-space distortion zone appears in Doraemon and Parallel Journey to the West. The time machine said that time and space had the first weightlessness, time and space were turbulent, and no new history was created.