Did you know? Lopunny was hand-crafted by Arceus Herself to be perfect sexual partners for humans? It's been discovered their extremely frequent heat cycles are in fact similar in timeframe to human women's menstruation cycles and while their desire to mate drives them to seek out any suitable mate, invariably their increased vigorousness during leads to exhaustion their partners and the Lopunny being left unable to satisfy their needs - a problem not encountered when a Lopunny selects a human, due to the increased stamina potential of human males.
And that's not the end of it, their biological development has left them with both narrower vaginal passages than the overall average sized passage yet led to more muscly, stronger-walled passages than the average, meaning that even the most unimpressive male endowment will almost-certainly be more than enough to give his partner an incredibly memorable time. And even if the Lopunny is impregnated during every cycle, with the natural resistance of pokémon to injury and the like, she can carry the kitten to term and give birth and her vaginal passages will still stay as tight as the day she evolved. Unsubstantiated reports are rife this has led some male humans to ignore females entirely, to focus their attentions solely towards Lopunny.