Pan is one of the most mysterious Greek gods, whose origins stretch back before those of the Olympian deities and whose province is less clear. He is the pastoral, goat-footed god of nature, fertility, and spring, as well as a figure of rejoicing and wild frenzy. His name means "everything" or "everywhere," as well as being the origin of the word "panic."

In E. E. Cummings's poem "in Just-," Pan is "the goat-footed balloonMan" whose whistling symbolizes the coming of spring. The poet depicts a chaotic scene of childhood joy in which "the world is puddle-wonderful." This lack of order might cause the adult world to panic, but the god is on the side of the children as he joins in their riotous play.

Pan enhances the themes of the poem by drawing them together in one chaotic figure. Whereas the more orderly Olympian gods are responsible for music or hunting or wisdom, Pan's cluster of related domains tallies perfectly with the multiple themes of a poem which is about riotous play, the joy of childhood, and the coming of spring.