Those pokemon are Plusle and Minun. They are Generation 3 pokemon, who live in Hoenn. They resemble Pikachu, Pachurisu and Emolga, but have no confirmed connection. They are quite easy to catch in the R/S/E. They specialize in double battles. Hope I helped! They appear in many Hoenn and Sinnoh seasons. One prime example I can think of is when Dawn battles Plusle in Minun in the final season of Sinnoh.
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