There's a double decker bus driving down the street full of passengers. On the lower level of the bus, everyone's having a good time, talking, laughing, and singing along to the music playing.
On the upper part of the bus, Maynard is in a panic. He's screaming, terrified, and holding onto others as the bus moves along the street.
Finally, someone gets up and walks to the top of the bus to ask what's wrong. Maynard replies, "What's wrong? Well, you'd be screaming too if you didn't have a driver!"