They don't speak or seem phased by anything that goes on. The only time they show any real emotion, is when they smiles due to Butters healing her in the game. Several events also cause her to react in surprise, shock or disgust, an example being when they are set on fire during battle, however they are mute throughout all these and never makes a sound. In the ending he will speak once by simply saying, "Screw you guys, I'm going home.