Jillian Vegan (voiced by Maryke Hendrikse) is Dark Vegan's daughter. She doesn't approve of her father's evil ways. She made friends with Johnny and has helped him save his world twice. As of the 4th Season, she is living comfortably on Earth, having successfully integrated into its culture. In her second appearance, it is revealed that she has a crush on Johnny, also once she was having a sleepover at his house and accidentally kissed him.
Jillian has dark green hair, unlike her father and mother. Her hair is pulled back and up in a ponytail curling tightly. She has almond-shaped blue eyes with bright blue eye-shadow and hot pink lipstick and sharp ears. She wears a hot pink floral shirt with a high collar and large white cuffs with dark purple pants with sharp white shoes. She also wears a red flower-like necklace over it. She also has two headbands, a white one with yellow spikes pointing up and possible her tiara, her second one is pale pink and half way up her hair and might be a large hair tie. In Dark Johnny, she wore a red one-piece swimsuit with matching sunglasses and purple-strapped sandals.
- Jillian once had a boyfriend but was forced to break-up with him because of her father.
- It's hinted that she's possibly 16 or around that age, because of when she said that if Johnny was 5 years older, she would kiss him.
- At the end of "Johnny in Outer Space" Johnny said that Jillian became the new leader of Vegandon, yet in Johnny X: The Final Ending (JX6-b) Dark Vegan was shown to have reclaimed leadership.
- There is a lot unknown about her.
- She has a crush on Johnny.
- Gil has a crush on Jillian.
- She wears pajamas with a design exactly like her shirt. They were first seen in Sleepover at Johnny's.
- Jillian is similar to Princess Leia from the Star Wars franchise since Leia is the daughter of Darth Vader, her father. The same relationship goes to Jillian and Dark Vegan.