My toddler learned three words in the last two days: cookie and thank you.
She’s decided that if she says thank you often enough this will lead to cookies. 
Our six-month old absolutely goes bonkers with laughter if someone coughs within earshot. He’ll laugh at other things too, but coughing is the big one. So, the wife always tells him it’s rude to laugh at someone that’s coughing, and of course, he stares at her all serious for about one second, then laughs again.