Straight from Joystiq straight from John Davis, the movie’s producer:
“… So this is the way I did it: The Sims, as you know, you can control your imaginary world, right? And in our movie, a young man, a 16 year old kid or a 14 year old kid and his friend get their hands on this thing called the Sims Infinity Pack, right, which is kind of this very strange video game store which was there just for that moment, and seemingly wasn’t and all that. But what they realize is that they can scan their world in, because this is the most life like, real Sims game ever. And as they are playing this they are all of a sudden realizing is what they are playing on the game is having an effect on the real world. So in effect, through the game, they are able to control their world. It’s wish fulfillment, and obviously it turns against them.”