Cory summed it up quite nicely:
FlyGuy is a n utterly enchanting little Flash app. In it, you are a pudgy salaryman who flys through an amazing, Hypercard-like monochrome line art fantasyland, sailing through the sky, through space, and eventually landing up in a tropical paradise where the monkey dances the hula all night long. Playing with this app made me feel like Tuttle in Brazil, having a dream of flying.
I especially enjoyed rocking out with the aliens.