Rebecca was disagreeing with me today about where she had left something (her cup, which was in the living room, where it's not supposed to be). I told her where it was and she just kept arguing. So I calmly pointed it out to her and she went over to it and said in a perfect little sing-song voice, "What-ev-er!" I couldn't help but laugh out loud at her!
Where does sarcasm fall in the developmental milestones?! :)