Neptunia is Ivan Prestonovich's and Chloe Carmichael's current fairy godmother. Unfortunately, due to her slight lack of intelligence, she sometimes, but rarely puts Ivan in danger with her wishes, or misinterprets the wording of a wish and grants it wrong, wreaking havoc, but she loves having fun as much as Cosmo, and at one point, her husband calls her the female equivalent of Cosmo. It is revealed a few times that she is smarter than Cosmo, considering her the third dumbest person in the universe, behind Cosmo and Timmy's Dad. Neptunia considers herself to be one of the most beautiful fairies in the Fairy World, and Timmy once said she was as pretty as Trixie Tang, if she became a fairy. Despite her slightly lower I.Q. compared to Astronov and a tenancy to argue with her husband, she really does love him and her godchild. She often goes along with Ivan's wishes unlike Astronov who is a little strict about them. Neptunia is a very good friend of Cosmo & Wanda, and she really likes their son, Poof. Alongside Astronov, she was one of the most unpopular students when she was at school in Fairy World. Neptunia used to dislike Wanda's ex-boyfriend, Juandissimo, because of him bullying her future husband in school, but she eventually became nicer to him after he and Blonda became a couple.
Neptunia has dark blue hair and dark green eyes. Like all fairy godparents, she has a crown floating above her head, carries a magic wand, and has fly-like wings which enable her to float. She has hair resembling Trixie Tang's hair. Neptunia wears a bright red dress and black heels, and uses red lipstick. When living with Mama Cosma and Cosmo after temporarily breaking up with Astronov in "Spouse Swapped!", Neptunia gets a new outfit that bears a resemblance Star and Twinkle's clothing from "Apartnership!", consisting of white boots, a white skirt and a white short shirt with no sleeves, but she soon goes back to her regular clothing after re-marrying Astronov. Neptunia's body is almost the same as Tooth Fairy's, except slightly shorter.
Back in High School, Neptunia looked different and more nerdy. She had light brown hair with pigtails, light pink lipstick, freckles and braces similar to Chester McBadbat. She wore a blue shirt, a dark blue skirt and bright red shoes.
Her voice is very similar to Katara from Avatar: The Last Airbender and April O'Neil from the 2012 Teenage Mutant Ninja Turtles cartoon.
When disguised as a pet, she takes the form of a blue cat.
During High School, Neptunia was always flirting with Astronov, but he ignores her because he was mainly focused on Wanda. One day, Neptunia asked Astronov to the prom, but Astronov refused and explained a very nasty complaint about her, which put Neptunia in tears and she angrily slapped him, then took off. After graduation, she wasn't seen again. Years have passed, and after flying past a beauty pageant in Fairy World, Astronov went inside and take a look at the bachelorettes. The last one came by and caught Astronov's attention. When the pageant was over, Astronov quickly rushed to the last bachelorette and introduced himself. Little did he know, it was the formerly nerdy and new stylishly beautiful Neptunia, who still held an ill-will towards her High School love interest. Astronov quickly apologized for what happened back at the prom and decided to make it up to her. After a few dates, despite their different ranks of I.Q., their relationship grew stronger as soon as they got happily married.