My grandson #GS3 waved and said bye-bye to me. He mixes the occasional English word / phrase (always appropriate for the situation) with babbling (or maybe talking in Martian; our conversation time is too limited to see whether he has patterns).

Many years ago, one of my nieces would say an entire sentence in baby Martian. If you asked her what she said, she would repeat the exact same sentence. The only word of it I learned was "bobm", which was her word for "apple". But then she switched over to English pretty quickly and the Martian went away.