Particle Man simulates the the attraction of particles and nuclei in a cloud (HII region). The prototype was used to study particle interactions, star formation and nebula evolution coming from sources such as pulsars and black holes.
Different ways of playing the game creates different outcomes - high fusion rates can cause star formation and nebulae while low fusion can simulate star interaction.
The name directly parodizes the They Might Be Giants song "Particle Man."
Particle Man may be the Galactic editor, a mysterious editor which is absent from normal gameplay. The editor may have once been in the demo of Spore, but was removed and now it could be the prototype.