As you play through the pizza levels, you will come across a stage where you have to deliver pizzas quickly before a UFO hovers over and destroys the house.
For this achievement, you must save several of the houses (deliver the pizza before the UFO gets there). Each attempt of the level gives you 3 or 4 chances to save a house. To earn this quickly, keep restarting after each play (complete the level or lose) until you save enough houses.