Raichu evolves into.....Pikachu
You know, now that I say that, it would be kinda neat to have a dual nature kind of pokemon that would 'evolve' every 5-10 levels into its alternate form and back again. Like, there could be two kinds coded into the game so that at max level you could end up with either type.
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There is no shame in not knowing; the shame lies in not finding out