I was in the car with the family, and the two younger ones were singing. Not whole songs, mind you, but just a couple of lines. First was "Workshop, baby, it's my life. I'm trying something out." Then it was "I wanna cross the line." Both lines are from the movie, Fruit Fly.
But the interesting thing I notices was the way my youngest, who is still learning to talk, pronounced the latter. It came out of his mouth as "Me wanna coss da yine." Most of that is simple mispronunciation that comes with toddlerhood. I remember, for example, that my oldest used to say "McDondants" instead of McDonalds, and my middle child used to call her brother "Eee-ah" because she couldn't manage the consonants in his name. But then there's the fact that he started with the word "me" instead of "I."
One aspect of his speech pattern, and this is fairly common, is that he uses the objective "me" instead of the subjective "I." He'll say, "Me hungry" or "Look what me do." But in singing the song, or the line from it, he already had the line constructed. He was repeating what he had already heard. And yet instead of literally repeating it, he translated it into his own version of the language.
I'd be curious to know what that sort of behavior tells us about psycholinguistics.