I love all the subtle changes in their facial expressions, it is very little but it does so much to give a certain liveliness to an otherwise static animation. My favourite of those subtle changes is definitely gotta be the red pupil glow during the lazer bit, the satisfied look on her face after hearing the answer is quite iconic too though, also kind of hilariously indifferent.
It's not much but it does what it does, whatever that is. The moderately trippy dialogue here will totally get stuck in my head for a while.