In a rarely shown first season episode, it's revealed that "Kimmy Gibbler" is actually the result of a transporter accident that merged Kimberly Tanner (an unseen fourth Tanner sister) and Giblet (the Tanners' beloved pet hamster) into a single entity.
Unable to split the amalgam back into its constituent parts, they reluctantly allowed "Kimmy" to stay in their backyard storage shed under the pretense that it was "another house in the neighborhood."
Every visit by "Kimmy" is a painful reminder of their tragic loss and the hostility they show her is, in truth, just the misplaced anger of grief.
Also, her smelly feet are pretty gross.
Fun Fact: the premise for the Voyager episode "Tuvix" was pitched to that show's producers as "Kimmy Gibbler, done right."
Unable to split the amalgam back into its constituent parts, they reluctantly allowed "Kimmy" to stay in their backyard storage shed under the pretense that it was "another house in the neighborhood."
Every visit by "Kimmy" is a painful reminder of their tragic loss and the hostility they show her is, in truth, just the misplaced anger of grief.
Also, her smelly feet are pretty gross.
Fun Fact: the premise for the Voyager episode "Tuvix" was pitched to that show's producers as "Kimmy Gibbler, done right."