My experience has been 3 infected sims show up as 'welcome wagon'. If you interact/let them in, one of them puts fruit into your fridge but the planting is not always. The 'feds' show up if you've had the welcoming thing. They will take your fridge even if your sim removes the fruit in advance into their inventory. As far as the outfits go, they were in their MIB ones only around the time the pack released. For a long time now the guy agents have been in women's clothes and gal agents have been in men's clothes. The only consistent thing has been sunglasses. The last time I played the story (a year or more ago) the fruit were irrelevant to completing it.