This wasn't super creative, but way back in time, I was on a local tinymud and a number of us starting writing bot NPCs for it. I built a bartender bot that eventually would remember drinks, tell jokes, and more. One day another bot came into the bar and got into an extended exchange of insults with the bartender bot. We were kind of dumbfounded watching these blocks of switch statements have a very real-looking conversation in front of us.