My oldest daughter discovered lying recently. I'm not sure how it happened exactly- whether she learned it by example from the kids at her preschool, or whether she developed it all on her own out of a simple desire to avoid getting a time-out.
But either way, she's definitely started doing it. If I tell her to stop fussing about not getting a lollipop, she'll keep right on fussing but she'll change the official reason for it. So instead of saying “I want a lollipop, I want a lollipop,” she'll start telling me she misses her friends or that she's cold. And then if I ask her what would make it better, can you guess what the answer is? That's right- a lollipop!