I’m surprised that most of the conversation regarding time travel themed anime (and sometimes parallel and alternate worlds) haven’t really touched on Doraemon.
The series is an episodic one, meaning there aren’t really much continuity between episodes, but at least if we don’t follow the TV series, there are various movies that can be talked about.
The movies mostly involve either time travel, the characters being trapped on an alternate world due to time-space mishaps or combination of the two.
The original 1980 movie, for example, involves a dinosaur fossil which was turned back into a fertile egg by one of the gadgets (Time Wrap), and that dinosaur was then brought back to 100 million years ago to the Late Cretaceous era so it can live with other dinosaurs. The antagonists of the movie would be a group of dinosaur hunters travelling from the 24th century who wanted the fossil to their collections. This movie was then remade in 2006.
The second movie is basically an isekai story. The dimension of the main character’s bedroom was somehow connected to a spaceship escaping from a destroyed planet due to an accident involving the ship. The main characters would then meet the people from the other planet and would have an adventure in that planet. This movie would be remade in 2009.
The series might not really seen fame in English speaking regions, but it’s probably known as one of the more popular anime series in Asia.
Also note that the isekai part is in quotation marks, since they don’t really do isekai stories, with probably an exception for Spaceblazer (movie #2) which is about separate dimensions being connected to each other.
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