According to uncovered scripts, Julie was a rainbow monster that was said to have lived in the outskirts of Home in the mirthful mountains ("A Darling Broadcast.") but who sought out a life of her own and moved away to the neighborhood. Julie reflects her namesake, which is to say overtly jubilant, excitable, optimistic, and undeniably joyful.

Many of her skits and activities centered around playing games, whether they were as familiar as jump rope and hopscotch or simply made up on a whim. ( See ‘The Welcome Home Wishbook.’ ) She was often depicted with Frank as a comedic foil, on merchandise and advertising. In the storybook record, "Happy Haunting to Boo and Yours," and well as various Marlo branded Looky-Loo books, it is implied Julie and Frank could be a couple. Other pieces of uncovered media frequently depicting them together could also serve to reinforce this idea. Her family was known as a "band" of rainbow monsters called The Joyfuls, of which it was implied she could have been apart of. The band consisted of Franny Joyful, Jonesy Joyful, and Bea Joyful. Although they appear in some pieces of media, they did not live in Home.

Julie and her siblings are fictional creatures called rainbow monsters, which were characterized by their long horns, big hair, musical ability, and ties with nature. Each one had their own monochromatic color palettes, with the exception being Julie who was polychromatic. It’s implied that these creatures control the weather and environment, with Julie herself being able to speak to flowers in order to make them bloom. Hibernation may be another descriptor of this cartoon species, as uncovered media surrounding the holiday of “Homewarming” depicted Julie hibernating throughout the winter. Akin to Barnaby, Julie’s paws also have hearts at the bottom. Julie is believed to be a puppet operated by one handler.