Critics have compared Stuart's life as a mouse entering a human world to that of an adolescent toward adulthood; which means that he is probably in his late teens or early 20s.
Mr. Little is supportive of his family, encouraging Stuart to see the bright side of bad situations and telling him the importance of perseverance.
She demonstrates DIY skills in Stuart Little 3: Call of the Wild when she makes improvements to the family's lakeside cabin.
Snowbell (voiced by Nathan Lane in the first two films, Quinton Flynn and Kevin Schon in the animated series and Stuart Little 3: Call of the Wild) is the family's Persian cat, Stuart's best friend and a former member of Smokey's alley cat gang.
Snowbell has further adventures camping in Stuart Little 3: Call of the Wild, until he is eventually kidnapped by a mysterious beast.
Stuart invites Harriet to go on a date with him in a miniature canoe, but discovers that it has been played with by the local children when they arrive.
LeRoy is a fat, lazy 12-year-old boy who is the owner of the Lillian B. Womwrath, a model sailboat which always managed to beat the other competitors in the Central Park boat race.
Margalo (voiced by Melanie Griffith in the second film and Rachael Harris in the animated series) is a young anthropomorphic yellow canary, one of Stuart's closest friends, and his love interest.
She saves Stuart's life when he stumbles onto a garbage barge, and is warned of Snowbell's plot to eat her and flies away from the Littles'.
His personal goal throughout the series is to cure his hunger, which involves him attempting to eat Stuart or digging for scraps in the city.
He later returned as a supporting character and Stuart, George and Martha's uncle in the animated series where it is revealed he has bought a farm, which Stuart and his family visit in the episode "A Little Bit Country", as well as a hotel that was thought to be haunted in the episode "A Little Vacation".
Smokey (voiced by Chazz Palminteri) is a Chartreux with a Mafia-like personality who is the main antagonist and the leader of the alley cats.
Smokey was defeated by Stuart at the end of the film when he knocked him out of a tree, causing him to be chased away by a horde of dogs.
Red (voiced by David Alan Grier) is a ginger American Shorthair tomcat and one of Smokey's henchcats.
Mr. Reginald "Reggie" Stout (voiced by Bruno Kirby) is Camille's husband and Stuart's fake father.
Camille reappeared in Stuart Little: The Journey Home for the Game Boy Color along with her husband Reginald in a driving stage.
He appears to be very passionate about boat racing despite his young age, and he is depicted as being rude, inconsiderate, and overly competitive.
Mrs. Keeper (portrayed by Julia Sweeney) is the head of the New York City Public Orphanage where Stuart was raised.
He took Margalo in when she was young and raised her to be his personal slave, forcing her to steal various objects, including Mrs. Little's wedding ring.
Early designs of the Falcon originally had him walking on both feet in an anthropomorphic fashion while wearing a necklace beaded with valuables he has initially stolen.
[7] The Falcon returned in the animated series in the episode "A Little Bit Country", determined to get revenge on Stuart.
An unnamed Indian-American taxi driver (portrayed by Ronobir Lahiri) drives the Little family around the city in search of Stuart.
Richard "Rick" Ruckus (voiced by Matt Kaminsky) is a pro skater whom George and Stuart are big fans of.
In the episode "Life, Liberty and the Pursuit of Taco Tuesday", he ran for the position of Class Officer, but his campaign was unintentionally sabotaged by Stuart, George, and Will.
After a couple of failed attempts to push their efforts back, Larry eventually admits that he only ran to get out of gym class early and favors a vote for Stuart.
Ginger (voiced by Julie Nathanson) is a female cat whom Snowbell develops a crush on in the episode "A Little Too Fast".
Reeko (voiced by Wayne Brady) is a smooth-talking anthropomorphic skunk and the Beast's former servant who befriends Stuart.
The Beast (voiced by Virginia Madsen) is a ferocious and ruthless female cougar, Reeko's master, and the tyrannical ruler of the forest of Lake Garland and the main antagonist.
She forced Reeko in particular to also bring her food, most likely due to him being late in doing so and plotted to make a rug out of Snowbell's fur.
Troopmaster Bickle (voiced by Peter MacNicol) is the slightly overweight, clumsy, comical, yet well-intentioned leader of the Lake Scouts.