I've been noticing that my sweet daughter is now being influenced by her peers, yes, her 3 year old peers. She has started to say new words and stick her tongue out (gasp!) and other actions that I prefer her not to do and we definitely don't allow in our home. If I see her copying a bad behavior, I remind her that we don't act like that in our home and if it happens later in the day/night we talk about where she learned this behavior and why we don't act that way. I really didn't expect to see this at such a young age!!
Here is an article that was helpful: