Marissa McKenze is the best friend of Sammy. She debuted in Sammy Keyes and the Hotel Thief, the first book.
Being the daughter of two workaholic parents, Marissa seems to always be away from her parents who are working until eight o'clock at night. Her parents had given her cash and a credit card to spend money on. Sammy and Marissa have been friends since third grade, and because of Marissa's wealth, has offered to buy Sammy Double Dynamos and Juicers. She was Sammy's first friend to learn of Sammy's situation. Grams (Rita Keyes) thinks that Marissa's parents spoiling her is compensation for them never being home.
Marissa can sometimes get nervous, doing a twitch called the McKenze Dance. She screams when a lizard is loose, and she is sort of cowardly. Marissa has had a crush on Danny Urbanski since elementary school, and even when he was kissing Heather, she was obsessed and was "stalking his house". After Danny was arrested for beating up a man on Halloween night, Marissa's judgement had been clouded because of her crush, and she was angry with Sammy for reporting him in. But it turned out that Danny had beaten the guy up, and she was able to stand up to him and let go of her feelings, and started dating billy Pratt
Marissa can be quite talkative; at a hospital in Los Angelas, she was in the waiting room jabbering away to some stranger about Sammy showing off her underwear at Trouvet's.
When Sammy drags her into going to weird or scary places she is reluctant and nervous. But when she is taking Sammy somewhere, and Sammy doesn't want to go, Marissa will remind her of the times when she was dragged to places.
When Marissa's family has financial issues, she and Mikey move into Hudson's and become closer.
Marissa has more knowledge of people in pop culture than Sammy does, pointing out numerous celebrities in Hollywood, which Sammy didn't know of or care about. She is more girly than Sammy, and she usually brings dresses for her and Sammy to wear in case of special occasions. Marissa tends to question things that Sammy is trying to point out to her. Marissa downplays her wealth heavily, sometimes criticizing her parents for working too hard and not paying enough attention to their children.
- Yolanda McKenze- Mother
- Bob McKenze- Father
- Mikey McKenze- Younger Brother
- Brandon McKenze- Older Cousin
- Bruce McKenze- Uncle
- Nob McKenze- Aunt
- Marissa's temperament has been described as Sanguine.
- Marissa and her family have the most known amount of relatives.