When they don't hear what you just said and reply to what they assumed you were going to say. Alternatively, they ask you to repeat yourself because they short circuited when you didn't say what they assumed you were going to say

How about this one, when they expect you to know what they're going to say. The subject of the sentence they want to say is at the tip of their tongue and they ask you what it is. How should I know? You haven't given me the verb and object yet and you expect me to tell you who or what did the thing when I don't know what thing they did yet

Or when they give you very vague clues to what they're looking for. I had someone ask me today what the movie about penguins is called. There are a lot of movies about penguins. Fortunately, my first guess was right (Happy Feet). And my Mom frequently asks what show I used to watch. There are lots of shows i used to watch, I'm sure there are some I don't even remember.