Thank you, Please and Are Doing?

Sam has started to say "Thank you Mommy" and "Thank you Daddy" spontaneously for many things and it just warms our hearts. He's also getting much better at saying please, though his new favorite phrase is "Are doing?" as in "What are you doing?" with all the inflection of the full sentence. He's also getting better at saying people's names, though the letter "L" still eludes him...