What's the last thing to go through a fly's head as it hits the windshield of a car going 80 mph? Its butt.
Fly's Last Thought
Explanation
Explain Bear
Okay, so imagine a fly cruisin' along, right? Then BAM! It smacks into a windshield. The joke is that the last thing the fly thinks about ain't some deep thought, it's literally its own butt because that's the part of the fly that hits the windshield last since the windshield is going fast. You probably didn't know that flies are among the fastest insects in the world.