|The cast of Watchmen|
Universe Man is Doctor Manhattan. In Particle Man, Universe Man is called "size of the entire universe man". This could be saying Doctor Manhattan has powers that can operate on the level on the universe or he is the most powerful man in the universe. This seem supported by Doctor Manhattan repeated godlike acts such as ending the Vietnam War single handily, creating matter out of nothing and surviving being killed several times. Universe Man's "watch with a minute hand, millennium hand and an eon hand" might be a metaphor for Doctor Manhattan losing his humanity and becoming apathetic to human suffering.
Triangle Man is Ozymandias. Triangle Man is constantly described as winning in the song. Ozymandias ultimately wins in the end. He is also described as beating Particle Man and Person Man, but I'll get to that later on.
Particle Man is the Comedian. In the song, narrator (when referring to Particle Man) says "What's he like? It's not important". This could being referring to the government ignoring the fact the Comedian is a ruthless psychopath since he gets the job done. Also the song, asks "When he's underwater, does he get wet? Or does the water get him instead?" In the context of the theory, this question asks if the society made the Comedian worse or did the Comedian make society worse? Finally, it is mentioned in Particle Man "Triangle man hates Particle Man. They have a fight, Triangle wins." and the Comedian is revealed to have been killed by Ozymandias.
Person Man is Rorschach. The song asks if Person Man "is ... depressed or ... a mess?" referencing his mental illness. Person Man is called "degraded man" and Rorschach is repeatedly contempt and disrespect by others (especially Sally Jupiter). Triangle Man is described as defeating Person Man. Ozymandias defeats Rorschach two times: in an actual fight and in the fact Rorschach is killed to help Ozymandias' plans.