When you type sentences for him, Nano will learn and say things back to you. The more you type, the more words he will know. He will probably start to say some pretty crazy things. Try telling him a story. He likes stories a lot. You can shift-click the green flag for 'Turbo Mode' if he starts getting slow to respond.
This is based on my earlier project, Lola learns from you. Lola learns words separated by spaces; but Nano learns 'chunks' of letters and which letter can follow each chunk. You can go in and alter the length of the chunks; very short chunks will make Nano say gibberish; long chunks will make him just repeat what you say. Currently the chunk length is set to four.