What had happened is that when you and your girlfriend (Lisa) had gone in the store and she had been looking around while you were in the photo booth. It was after you had pressed the start button that it had caused you both to change without her noticing what was happening.
When it first started Lisa is 15 and still in tenth grade but what happened is that she was becoming older. What was happening is for every 3 years you lose Lisa gains 1 year.
By the time you have become a fetus Lisa had become a 20 and she looks to be pregnant about 3 months along. What had also happened is that because your at a early development stage your gender isn't set yet.
The clerk asked Lisa what she was having a boy or a girl. She says that it is to early but she says that she hoping that she has a girl.