Dunno why this came to mind, but for Garchomp, I was thinking a surprisingly geeky gal. She lives high in Mt. Coronet, and barely talks to anybody. She absolutely LOVES anything Fantasy, and her cave walls are coated in fanart for her favorite shows, and she's currently writing her own original story. But, she feels like she's missing something, until the Player comes along and gives her some inspiration. Out of both gratitude and crippling loneliness, that's when she offers the frisky stuff.