Conversation so far:
Was Mewtwo in a book?
Mewtwo has appeared as a central character in several books related to the Pokémon franchise.
What was the first book Mewtwo was in?
Mewtwo Strikes Back
What was the next book Mewtwo was in?
Mewtwo Returns
Was Mewtwo a popular character?
Mewtwo is regarded as one of the series' strongest Pokémon; it was also one of the most popular pokemon for some time.

Question: Are there any other interesting aspects about this article?
Self-contained rewrite: Are there any other interesting aspects about Mewtwo?