Stewart is an elephant who, although larger in size, looks up to Marsupilami as a big brother (Mars calls him "Stewie" for short, much to his annoyance, and the one time the small, spotted animal called him by the proper title "Stewart", the elephant was Bugs-Bunnied and said "That's Stewie... Oh! You know what I mean!", and Mars told him to deal with it, because he's a grown up). In "Mars' Problem Pachedurm", Stewart reveales he truely is a problem, as he keeps bothering Mars when he doesn't invite the elephant over to play games, and ignores him in hopes he'd go away. Stewart is also a pest for his many fears (narosis, as far as Marsupilami can tell): Open Spaces, Closed Spaces, his Aunt Lillian's Tomato Soup, Drowning, Algae, Piranhas, Heights, Flying, Spiders and insects (Mars figured this is Stewart's greatest fear, and scares the elephant with an impression of a spider, tail as a web, to show spiders are harmless... except to flies), Shadows (most oftenly his own shadow, or Mars'), but of all the fears he concerd in one day of "Marsupilami's School of No-More Narosis", Stewart, as all elephants, can never get over his fear of mice, as he figures rodents have germs, rabies and... of all things... cooties! Whenever Stewart is scared and/or grossed out, he runs streight up to Marsupilami, even if it means climbing the tree he lives in and distroying the nest in the process. Also, Stewart is such a nervous wreck that he loses his memory, which is an elephant's greatest shame, and can't remember what he's not afraid of or the one person who liked him besides his parents.
In his first appearance Cropsy Turvy (though the episodes lack timeline order), Stewart claims Marsupilami is always trying to scare him, usually though campfire stories and pranks (if not one or the other), and Mars tells him it is called a "joke".
Stewart's memory seems to had improved in Spotless Records', as when Mars started to lose his spots from eating a bad melon, Stewart recalls a tour of unusual fruits and vegitables that he saw a tree of spotted fruit on the other side of the jungle that'll cure him, although he's not quite as able to remember the common train-of-thought (Mars:"Are you possitive you remember how to get to the fruit tree, Stewie?" Stewart: "That's Stewart,and elephants never forget any thing. <pause> What fruit tree?") and due to reluctance to come with because the long trip is his idea of "dangerous" (rodents, bugs, open/closed spaces, & Stewart confessed he has hay fever since the closed space they took is tall grass) and he only came with out of fear of being alone, he forgot to tell Mars before he ate the fruit that there might be side affects... like sneezing the spots off as soon as they grew back!