"Young, gifted, geek":
     Marshall is dedicated, aims towards amusement, and tends to think about ways of making money. He apparently dressed up as Principal Durst for Halloween and made a genetically engineered soap that turned his skin green.
Marshall has an overall carefree attitude and does not express himself emotionally. Aside from when he is caught up in a business venture, he is quite silly and without worry. When in a business venture, Marshall seems to lose sight of ethics but later realizes what he has done wrong and seeks to correct it.
Marshall has an older brother named Grant who also attended Blake Holsey.
Marshall's roommate is Lucas in room 32.

     In season one, Marshall deals with feelings of insecurity. While everyone picks on Lucas, people don't seem to notice Marshall or take him seriously. Marshall often acts as a moral compass for the group, alerting them of possible repercussions and is often disappointed when they push aside his prophecies.
     In season two, Marshall focuses on his future and looks for ways to increase his finances to help with college. This often leads him into problems with ethics as he falls prey to those with unscrupulous ideals. Marshall also ends up being on the short end of the stick whenever Corrine makes a mistake in her work.
Marshall becomes the lead singer of "Magnet 360", a band of Blake Holsey.
     In season three, Marshall's social status appears on the rise as he is gaining popularity from Magnet 360. Despite falling prey to Diana Music, he becomes Corrine's boyfriend which reveals Marshall's ability to become jealous. Marshall still takes a fair amount of hazards from Corrine's attempts to gain his attention, however.

In the mirror!universe, Marshall is dark. He has an apathetic attitude taken to a negative perspective. When Corrine appears in the mirror!universe, mirror!Marshall virtually ignores her.
Controversy has arised in the fandom that leads some fans to believe that mirror!Marshall does not have a firm grasp on his emotions and is somewhat of a jealous character. The theory is that he pushed the mirror, in an attempt to break it, that was the way for Corrine to return to the normal universe so that she would stay and be with him.