We were told that the guinea pig we were getting was a "girl" and as one assumes that those who tell you know how to tell these thing, so one doesn't question it. So we all got use to calling her "her" "girly girly" and the likes and finally settled on a name "Jackie" we settled in to a happy life with our Jackie. But as Jackie began to grow beyond the size one would expect a female guinea pig to grow to and in fact as she more and more seemed to be the size of a male, one began to wonder. So after much in dept research and and a careful examination of Jackie (which she didn't really appreciate) our suspicions were confirmed, yes in face our girl was, beyond any doubt a boy. So now we struggle to call him "him and not "her" but we are sure with a little time he will be fine and i guess that should he have any problems we can always get him therapy. He is still Jackie!