When my oldest was about 30 months, we took hum to Toys R Us, and he learned the term 'toy store'. That was fresh on his mind a few days later when he was being very demanding, and I said to him, fully believing that he wouldn't understand, "The world is not your oyster!"
He responded, "The world is not my toystore?"
His response was as close as a 2-year old can get to understanding what I said to him. He was amazing.