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it's interesting how often Pokemon from the first two gens are actually both biped and quadroped but are only depicted one way.
For example, all 3 Johto starters primarily operate on 4 legs but Typhlosion and Feraligatr stand up on two legs to look more imposing. It's technically the only time we've ever had all three starters be quadroped but looking only at official art or in-battle animations you wouldn't know it