Oki's words

Oki is full of words these days.
He constantly surprises me with how much he remembers. The other day he said "duck billed platypus" when he saw a sticker of one we'd been playing with days ago. How can he remember such a sequence of words?
He is also good at repeating what we say, which can be very entertaining! Just before I put him to bed tonight, he said to me his new word of the day "dodgy punter". 
I said, "Yes, dodgy punter is sleepy too. Good night" He makes me laugh that little boy :D