He is the erudite, mature, and sensitive twin who gets straight "A"s (although he did avoid a "C" in wood shop by changing it to a pass/fail class). He often plays along with his brother's crazy schemes. He shows less interest in girls than his brother, but he too gets almost as much as Zack (including the boys' best friend, Sam Riveter), because girls tend to be more drawn to his sensitivity and intelligence. Zack usually calls him a nerd, though Cody would prefer "educationally gifted." London used him on various occasions to do her school work. He has a girlfriend named Barbara Brownstein, but they are constantly competing on who is smarter. He has shown a passion for baking, cleaning, and cooking, as well as mime and dance. He also has a passion for stamp collecting, being the president of his school's stamp club, and is known for coining the motto of the club, "You can't lick us", to which Zack disgustingly replied, "Well, here's my motto, 'my brother's a nerd.'" Cody tends to be more sensitive, caring and better behaved than his brother, but he is not perfect; he has a meaner and greedier side, portrayed in several episodes. Cody is known for doing well in school. He has gone to math camp before, camped out as a wilderness scout, and has won a spelling bee. He can be easily frightened, and is often worse at physical activities than his brother (Zack routinely outperformed him in woodshop, and as a scout, he was excellent at memorizing the information in the handbook, but did far more poorly at actual camping activities than Zack.) He had also won the election for 8th grade class president, as seen in the episode Election and written a letter to city hall for saving a public park (which bored city hall unimaginably). It is revealed in Foiled Again that the Martin family own a gold fish because Cody said "Take the goldfish out of the coffee pot and put it back in this." He and Zack entered a game show called "Risk it all" but lost because Zack got too tired by the end and fell asleep while spelling "dog" with block letters.
Like Zack, he inherited some musical talents from his parents. It is seen that he has received singing talents like his mother, as seen in the episode, Lip-Syncing in the Rain and Sleepover Suite, and is shown to have an acting ability, yet in "The Suite Life Goes Hollywood", Cody has stage fright. In addition to vocal ability, Cody plays the French horn and violin. In contrast to Zack, Cody is closer to his mother and heeds her advice. Cody is also more sensitive than Zack, He is always stuck to his security blanket called blankie.
His favorite United States President is Jimmy Carter because he builds houses for the poor, and he was valedictorian of his eighth grade class.
In Season 1, Cody tends to be as much of a troublemaker as Zack. As the show progresses, his character develops into a type who generally only gets in trouble by mistake or (more often) due to Zack's influence (although he is not perfect, and sometimes makes mistakes of his own, without Zack's influence.) Additionally, Cody is often the victim of various sight gags (which range from humorous to sometimes traumatic). Some examples include being pushed in horse feces, getting trampled, and being frozen in ice (which he does not remember). In "Big Hair & Baseball" it is revealed that he has astigmatism. Cody is While at school on board the S.S. Tipton, Cody is the ship's towel boy. He has a crush on a new character, Bailey Pickett, though Zack claims that he, "You [Cody] and Bailey wouldn't have heat if you were in a sauna…that was on fire…in a volcano…on the sun."