The Mutant in Hospital Gown is a monster kept in the Facility. Since the Mutants are listed on the whiteboard, this monster may have been included with them due to it being a mutant as well, but it later exits out of its own cube during the Purge where it tries to attack Marty.
Physical Description & AttributesEdit
While it resembles the Mutants in appearance, it is slightly different from them. This mutant's face is more grotesquely deformed than the other Mutants' faces. Unlike the other Mutants who are seen wearing orange and red jumpsuits and straight jackets, this creature wears a hospital gown. It is released during the Purge and it tries to attack Marty, but he shoots it in the head right through the eye before it can attack him, killing the mutant.
It maybe a reference to the mutant from Septic as it bears uncanny resemblance to him as they are both mutants in gowns originating from hospitals. It may be a reference to other horror films such as Mutants and The Hills Have Eyes, horror films about people who have been infected by horrible viruses or even real real life cases viruses and flesh eating bacteria.