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I had 5 Pokemon in my FireRed run, and was debating which to use to fill up the sixth place when this glittery fucker popped out in the Pokemon Mansion. First ever shiny, naturally she was a sign from Arceus to train Raticate. Ignored my Master Ball, caught her regardless, and after a short bit of grinding to get her up to speed with the others she earned her keep. Never wanted to train an early rodent before then, and I still don't, but Raticate is sis/bro tier.
Plus the color matches with the old nursery rhyme about the bubonic plague, which is definitely a plus for a rat pokemon.