When she was younger, she would sing commercial jingles. At first it was just a few lines from the commercial, then it progressed to the whole thing. One of her favorites is the "Five Dollar Footlong" song from the Subway commercials.
This morning, I heard her reciting something familiar. I had her repeat it, and I almost fell over laughing. I made her do it again so I could get a video, and here it is: