Stuart on a pet has one dominant cultural anchor: Stuart Little, E.B. White's 1945 children's novel about a mouse born into a New York City family, adapted into the beloved 1999 film. Any small pet — particularly a mouse, rat, hamster, or small white dog — named Stuart is almost certainly paying tribute to that character, whether the owner knows it consciously or not.
Stuart Little: The Source
E.B. White's Stuart is resourceful, brave, and slightly formal — a small creature with enormous dignity. The 1999 Sony film starring Michael J. Fox as the voice of Stuart cemented the name in a generation's consciousness. Stuart on a small dog or cat carries that combination of miniature scale and outsize personality that the character embodies perfectly. Maltese dogs, white and small, are ideal Stuarts.
The Human Name Register
Stuart (from Old English "steward") was a moderately popular American baby name through the mid-twentieth century — now vintage enough to feel slightly formal on a person, perfectly calibrated for the ironic-human-name-on-a-pet aesthetic. The human name Stuart carries that same slightly stiff, endearingly earnest quality that makes it charming on an animal.
The Counter-Reading: Size Expectations
Stuart on a large dog creates the same productive irony as naming a Great Dane Tiny , the mismatch between name expectation and physical reality becomes the personality. Great Danes named Stuart would have their own very particular fan club.