This is what all the pokedex enteries has to say about RK9 & Mew (I'll be useing the sprites from Crystal!) B_F edit: No, you won't. More unnecessary images? No thanks. AND you're hotlinking anyway. Way to go for manners.
RK9:
Blue/Red & LG: A Pokémon that has been admired since the past for its beauty. It runs agiley, as if on wings.
Yellow: A legendary Pokémon in China. Many people are charmed by its grace and beauty while running.
FR: A Pokémon that is described in Chinese legends. It is said to race at an unbelievable speed.
Gold: This legendary Chinese Pokémon is considered magnificent. Many people are enchanted by its grand mane.
Silver: Its magnificent bark conveys a sense of majesty. Anyone hearing it but cant grovel before it.
Crystal: An ancient picture scroll shows that people were attracted to its movement as it ran through prairies.
Ruby/Sapphire: Arcanine is known for its high speed. It is said to be capable of running over 6,200 miles in a single day and night. The fire that blazes wildly within this Pokémon's body is its source of power.
Emerald: This fleet-footed Pokémon is said to run over 6,200 miles in a single day and night. The fire that blazes wildly within its body is its source of power.
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Mew:
Red/Blue & LG: So rare that it is still said to be a mirage by many experts. Only a few people have seen it worldwide.
Yellow: When viewed through a microscope, this Pokémon's short, fine, delicate hair can be seen.
FR: A Pokémon of South America that was though to have been extinct. It is very intelligent and learns any move.
Gold: Apparently, it appears only to those people who are pure of heart and have a strong desire to see it.
Silver: Its DNA is said to contain the genetic codes of all Pokémon, so it can use all kinds of techniques.
Crystal: Because it can learn any move, some people began research to see if it is the ancestor of all Pokémon.
Ruby/Sapphire: Mew is said to possess the genetic composition of all Pokémon. It is capable of making itself invisible at will, so it entirely avoids notice even if it approaches people.
Emerald: A Mew is said to possess the genes of all Pokémon. It is capable of making itself invisible at will, so it entirely avoids notice even if it approaches people.
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You see I don't see anything to do with RK9 & Mew being rivals!
Just Mewtwo (which I've met the VA of) & Mew!