Alan is hanging out with Alice alone in the forest when they get caught by Alan's girlfriend Betty. Feeling agitated, Betty confronts them, asking what they two were doing there. Wanting to make Betty even more jealous, Alice mischievously replies,
Gee, I wonder what we could've been doing. I think you can imagine what it was.
Hey! You don't know what yourself could've been doing? I wonder if this type of playful expressions are natural.