She is voiced by (renowned child now-teen) actress Anna Sophia Robb (Because of Winn-Dixie, Soul Surfer, Race to Witch Mountain, The Reaping, Charlie and the Chocolate Factory, Bridge to Terabithia) in her first appearance, and later by Krista Swan.
Vlad, desperately lonely despite his wealth, conducted a series of experiments with the aim of creating the perfect half-ghost son for himself. He tried to accomplish this by making clones of Danny Phantom, using Danny's half-ghost DNA. All of his attempts failed except for one, which resulted in a half-ghost girl whom Vlad named Danielle. Vlad never faltered in showing love and affection to his "daughter," and Dani never faltered in her desire to serve her "father."
In "Kindred Spirits," Vlad sent Dani on a mission to capture Danny so that Vlad could take the DNA samples he needed for his perfect clone. She snuck into Danny's room and waited for him in her human form, reading his comic books. When he came, she introduced herself to him as Danielle, his third cousin once removed, and they quickly formed a bond despite Danny's suspicion. Later, Dani succeeded in bringing Danny to Vlad. She then found out that the "perfect clone" Vlad was trying to create was was not her, but a male clone designed to be just like Danny. Together, they put a stop to Vlad's plan. Dani then leaves to travel on her own, promising to return.
In "D-Stabilized," Dani's instability finally caught up to her, which would cause her body to spontaneously melt into a puddle of ectoplasm without warning. Dani returned to Amity Park, seeking Danny's help, but instead found Valerie. Valerie was working for Vlad, however, and tried to use Dani as a trap to find her real target, Danny Phantom. Valerie's plan worked, and she captured Danny, while Vlad took Dani. Danny convinced Valerie to let him go to find a cure for Dani, as she was half-human and Valerie didn't want Vlad to hurt humans. Using one of his parents' inventions, Danny rescues Dani and stabilizes her body using his father’s Ecto-Dejecto. She then attacks Vlad and, after defeating him, she once again leaves to roam the world.
Dani was seen briefly in "Phantom Planet" as one of the ghosts assisting Danny in turning the Earth intangible to save it from the Disasteroid.
As Danny's clone, Danielle shares some similarities with Danny. In her human form, like Danny, she bears a strong resemblance to her genetic mother, Maddie Fenton. She has the same skin color, eye color and hair color as Danny. She has the same hairstyle as him, with the back longer and in a ponytail. She wears a red beanie, red shorts (plain in "Kindred Spirits," and with a cameo pattern in "D-Stabilized"), a blue sweater/hoodie, and shoes of the same style as Danny's but blue.
In ghost form, her skin, hair, and costume are of the same color scheme as Danny's. Instead of a one-piece suit, she wears a matching shirt-and-pants set that reveals her midriff, with no belt. The right half of her shirt is white and the left half is black, divided diagonally down the middle, and she wears a white left glove and a black right glove. Her pants are black with streaks of white on the sides that come down to her boots. She has the same D emblem as Danny on her chest.
Danielle shares many of Danny's likes and personality traits. Unlike the other failed experiments, she is not mindless and doesn't mind voicing exactly how she feels. A very willful and somewhat tomboyish girl, she's a lot like Danny, only more cheerful and childish. She seems to have no concern with responsibility, and can be quite stubborn at times. She can also be quite naive, which is, in part, due to her limited existence so far.
She is about twelve years of age physically, but due to her being a clone, her actual age is possibly a few months at most. Because of her limited knowledge, Danielle is easily talked into obeying Vlad's commands, as she thought of him like a real father, and it wasn't until she met Danny that she realized that she was just one of Vlad's pawns.
- In her human form, Dani has the same hat as Chip Skylark from The Fairly OddParents, another TV show by Butch Hartman.
- Butch Hartman stated in a video that if the show had a fourth season, Danny's parents would have adopted Dani as their daughter making her Danny and Jazz's younger sister.
- Dani Phantom on Danny Phantom wiki