At first, the girl you're courting wants a donut. Despite the long queue, you queued and got it for her. Later on, she asks for a donut again, and this time you choose a donut shop that has no queue. Much later, you give her the money to buy it herself instead.
Yeah, I don't see the humor either. I was expecting it to progress. Like first she just wanted a donut, then something more expensive then in the last frame she'd want a ring or something like that... That would be funny. Not everyone!