We haven't had any long dialogues yet but I still crack up about this: when it was around 4pm and Spencer started singing, "good morning, good moorrning!" I replied, "It's not morning silly!" and he said, "Sleepy time?" I decided he needed a mid-day greeting so within a day he learned "konnichiwa!"
Also, one day it was late and he kept repeating, "Sleepy time!..... Sleepy time!" etc but I was busy so I didn't respond yet.. finally he said, "Hello???", first time he ever said hello in a question tone, it was so funny!