-When adding an NPC to your party, repeatedly click on him or her. They will say something either serious or funny. For example, Khalid says "Click on someone your own size". Each NPC says four things, then return to addressing you normally.
-Formore hidden comments from NPCs who cannot be in your party or you simply want the results faster, right click on their circle. A great example is a Flaming Fist officer who, if clicked enough on his circle, will say "You there! Give fifty pushups."
-Right click on non-humanoids (bears, kobolds, etc.) to listen to some hidden comments. For example, a black bear comment is "Boo Boo that looks like a good pickinick basket".