Nidoran is the only species of Pokemon that makes it obvious which ones are male and female. I came up with this idea when I thought about the lack of gender in Pokemon, and how Pokemon are all referred to as “it” and not “he” or “she” even when some of them seem very male or female. Take Goldeen, for instance. There is nothing even remotely male-seeming about that pokemon, yet some of them obviously must be boys, too. Or even better, most Chicorita are male, yet they look like distinctly female pokemon. There’s no way to tell. Except for Nidoran.