My DS2 loves Doc McStuffins and therefore, we do too. At his wellness check up last week he kept singing, "It's time for your check up, It's time for your check up." And anytime he gets hurt and then feels better... you guessed it, "I feel better, so much better..." As PP said, the songs ARE catchy! DS is also always asking if we "need a cuddle" if he thinks we are sad or tired.
We also like Octonauts. DH and I comment on how much we learn about sea life when watching!