Professor Utonium’s appearance is defined by clean, geometric lines and a deliberately “square” aesthetic that mirrors his orderly, scientific personality. His face is a nearly perfect rectangle, with a pronounced jawline and a confident, well-composed expression that rarely wavers from calm professionalism. His jet-black hair is styled into an immaculately straight part, emphasizing the angular symmetry of his features, and his thick, expressive eyebrows give him an air of both warmth and earnest intensity. While the series normally depicts him with simple black-dot eyes like most characters, he does briefly appear with distinctly blue eyes. He is almost always dressed in a crisp white lab coat—his signature look—complete with a pen or two tucked neatly into the breast pocket, suggesting constant readiness for scientific note-taking. Beneath the coat, he wears a classic white shirt and black tie, reinforcing his old-fashioned, slightly retro charm. His tall, narrow frame is accentuated by straight black pants and angular shoes, giving him a silhouette that is unmistakably formal and slightly exaggerated.

Blossom has long, fiery red-orange, waist-length hair with a triangular part and bangs and pink eyes. She wears a pink dress that has a black stripe in the middle with white tights and black Mary Janes. She has a red bow on the top of her head and a heart-shaped hair-clip that can be seen from behind. She's the mature one.

Bubbles is portrayed as having blonde hair in two pigtails and a neat, curved fashion and sky blue eyes. Her dresses are sky blue with a black-centered stripe and she wears white tights and black Mary Janes. The outro refers to her as "the joy and laughter," meaning that she is defined as very sweet in personality. Professor Utonium named her Bubbles for her cute, bubbly, and joyful attitude (which she revealed by giggling when he named Blossom). Her best friend is Octi, a stuffed octopus given to her by the Professor.

Buttercup has short black hair in a flip with a small triangular part on her forehead. She has lime green eyes and dresses in a lime green dress that has a black stripe in the middle of it. Buttercup also wears white tights and black Mary Jane shoes with her dress. Her special ingredient is spice and her signature color is light green. While Buttercup doesn't seem to have any special superpower different from her sisters, she is physically the strongest of the three girls. In the episode "Speed Demon" it was also revealed that she can fly the fastest out of all of her sisters. Her special ability is shown to be able to curl her tongue. She's the tough girl out of her sisters.