- MurderMen are like people, but are genetically engineered for murder and maximum destruction.
- Most of what they think about is centered around murder and how to better murder people.
- MurderMen are able to bite humans and quickly turn them into MurderMen themselves, or "MurderMan" them.
- Sometimes MurderMen just outright kill people, or "ManMurder" them.
- Once a victim has been MurderManned, they turn into a MurderMan within a few seconds to a few minutes, then begin obsessively wanting to murder all non-MurderMen in the vicinity.
- It is not clear if other species other than humans can be MurderManned. However, Croach the Tracker was infected with the Pleasure Being Virus, which is a strain of the MurderMen Virus in Dinner and a Groovy, so it is likely other species, at least those which use nanotech at a minimum, can be infected.
- It is also unknown if MurderMen can reproduce with other MurderMen, or if MurderMen all have human origins.
- There is a cure for humans newly MurderManned via "frying the bad nano" that causes the virus. It is unknown if this cure works on those who have been MurderManned for a long time. Harriet Alcott-Jiminy, aka The Troubleshooter, was on the team that helped develop the cure.
- Once cured of the MurderMen Virus, the subject is immune from further infection, even with sub-strains like the Pleasure Being Virus.
- Homocido sapiens is the Latin name for MurderMen.
- MurderMen are space-faring and capable of rational thought, but most of what they think about is murder.
- MurderMen still seem to possess their personalities and all their memories.
- In the graphic novel, the MurderMen's skin is gray, presumably having turned so after infection.
- In their Murderships, the MurderMen run Windows OS, and their WiFi password is "murder."
There was, briefly, a very tenuous Man-MurderMan treaty in effect, but the treaty was broken in Space-iversary and the MurderMen began invading Earth in Mayor's Retreat. The MurderMen's invasion of Earth was defeated by Cactoid Jim leading a cavalry of Mayors and the USSA forces, but not before many were killed including Gene Peeples' wife, Linda, and daughter, Erica in MurderMen. However, the Man-MurderMan war continued throughout other parts of space.
In Murder in His Place, MurderMen invade Mars and MurderMan several people, including Felton, who goes on to MurderMan Sparks Nevada, The Red Plains Rider, Chicky Sullivan, and Rebecca Rose Rushmore before being saved by The Troubleshooter. The Troubleshooter fries the bad nano that causes MurderManning and reverts them all back to normal.