Where do they pick this stuff up?

I've been told that kids are like sponges and I couldn't agree more. I just wonder where do they pick this stuff up? I know my three-year-old daughter takes after my husband and I, fellow day care kids, and of course television. But, on several occasions she has said things to me and I can't figure out where she heard or saw them? I'm obviously not paying as much attention as my daughter. Yesterday, she asked for my hand so I put out my hand. My daughter shook my hand and said, "Nice ta see ya." And then she pretended to leave out the front door. It was the cutest thing. I tried to recall having ever said "nice to see you" to anyone while she was around? Maybe it was on TV? My daughter has unfortunately started saying, "Whatever." I have to turn around to roll my eyes so she doesn't start doing that too. Another time, I asked my daughter if she wanted her jacket because it was cold outside. She replied, "It's not that cold, mommy." I felt like a teenager was talking to me. It's amazing how fast kids soak in the world around them and sometimes scary. I know I really need to pay more attention to what I say and do or my daughter's going to start using curse words she's heard from yours truly...