As you probably know, the first gen Pokémon games we got in the west, Red and Blue, were based on the Japanese Pokémon Blue, which was a revision of the original Japanese Pokémon Red and Green, including notably reworked sprites and graphics.
Here are some sprites from a CoroCoro edition that showcased the changes in the Japanese Pokémon Blue versior. It includes sprites that were altered in the final release. These are exclusive to this edition of the magazine and were never seen again.
More info & further reading: http://lavacutcontent.com/corocoro-comic-pokemon-blue/
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