A Man's Change

All of your guy friends are stood amused, staring at you. They begin smirhing and your girlfriend is stood in the corner wearing all of her clothes. 'What the Hell?' you think.
Suddenly all of you mates begin diving on you, taking it in turns to.. well, you get it.
Your girlfriend giggles loudly. You try to explain the situation to everybody who has a try, but you only get a part of the story across to each one. They decide to ignore it and after half an hour, your girlfriend tells them to leave. They are satisfied and do as she wishes.
Your girlfriend finally speaks to you, " Not that easy is it. Now time for your surprise!"