Is it possible to catch Riolu in Pokemon LeafGreen? Or is it only obtainable in Pearl, Platinum, Diamond, and further Gens?
No because Riolu and Lucario were not released at the time.
Riolu and Lucario were released in Generation IV, Pokémon Fire Red and Leaf Green are Generation III Games so it is impossible to catch a Riolu in Pokémon Leaf Green.
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You can't get Riolu in Pokemon LeafGreen. Because Riolu was realesed after LeafGreen. Riolu is a generation 4 Pokemon not generation 1,2 or 3.
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