Where did all these sentences come from??

Courtney has always been a mostly 2 word sentece girl. Lately it's been, "Happy Baby" everywhere she goes, or "I see" when she wants to see something. Yesterday we were driving and all of a sudden we hear, "I see a birdie outside!" And last night she came in the house and said, "I want my shoes off." And this morning she said, "I want a treat, Mom". I didn't know this child knew full sentences!