I had him be a Dungeon Master and start taking me through an adventure. Was very impressive and convincing (for the two minutes I was conversing), and the latency was really good. Felt very natural.
Hah- this is a great hackathon idea. I tried this concept just now and asked it (him?) to give a joke at the end. "What do you call an orc with two brain cells?... pregnant". Lol