It's amazing how kids learning to talk pick up colloquialisms. When we were on vacation, Xander was explaining something to me and after he was done, he said, "Get it, Mom? Get it?" The word "duh" just hung in the air, waiting to be said, but he didn't say it.
However, he still needs to work on his grammar and pronunciation.
"ambliance" = ambulance
"I amn't" = "I'm not"