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Just like how Donald mostly wears a sailor shirt, Della was typically sporting a pilot's outfit. In the past, she had short white hair and had both duck flippers. In the present, her left leg was cut off and replaced with a metal one made from rocket parts. During the ending of the season one finale, her hair grew much longer but was later cut back to normal after returning to earth.
Despite the fact she was initially missing in action, she was well-known for being a high-spirited, daring and courageous woman who loved going on adventure with her family. In many adventures, she has been shown to help others, and was a quick thinker that helped to get the family out of trouble, although she has also demonstrated that she can be quite a prankster, as shown in "The Secret(s) of Castle McDuck!". Unfortunately, her thrill-seeking personality often blinds her to the dangers and consequences of her rash selfish actions, which later resulted in her becoming lost in space. She is shown to sometimes be more level-headed compared to her brother Donald, due to his hot-headed personality. However, other times, they can switch roles and he can be the more reasonable one, such as when he tried to talk her out of going on an adventure when they had triplets on the way, making a good point that it was really not a good time for that. She's also frequently shown that she has the same short temper that he has, the only difference being that she's generally a bit better at keeping it under control.
Prior to the events of the series, she used to go adventuring with her brother and uncle.
Days before her sons hatched, Della – a passionate pilot and aspiring astronaut – took off with a spaceship built by Scrooge: The Spear of Selene. When she got caught in a cosmic storm, Scrooge tried to guide her through it, but contact with The Spear was lost, and Della hasn't been heard from since. Donald, blaming Scrooge for Della's disappearance, cut off all contact with his uncle and raised the triplets by himself, while Scrooge spent years trying to find his niece, until his board of directors cut the expenses.
Thus, she only appears on photos and paintings throughout most of the first season, making her first major appearance within the franchise in a series of flashback stories in issue #2 and #3 of the DuckTales comic book.
In the season one finale, she is shown to be alive and well on the Moon, unable to contact Earth; But she does manage to hook up a tv enough to find her family reunited with Scrooge.
Years after Scrooge had failed to find his niece, Della made it home using the renovated Spear of Selene, wear she reunited with her kids, her uncle, and her brother.
Scrooge McDuck is Della's uncle through his youngest sister, Hortense McDuck. Della and Scrooge are extremely close and have a strong father/daughter like bond due to their shared love for adventuring. She sees her uncle as a father figure.
Donald Duck is Della's twin brother. Despite their different views on adventures, Della and Donald are very close and they love each other very much. They always want to protect each other.
Huey,Dewey&Louie Duck are Della's sons whom she dosen't meet for almost 11 years.
Selene is Della's best friend.
Penumbra is Della's second best friend and former rival.
Lunaris is Della's arch-nemesis and greatest foe. At first, Della trusted Lunaris for letting her stay in Tranquility and treating her like a friend. However in truth, Lunaris was manipulating Della from the start and uses her as a pawn to achieve the rocket ship manual from her and start an invasion on Earth. After learning of Lunaris' true intentions, Della is shocked and horrified that he tricked her into giving him the rocket plans and he never cared about her at all. Della's trust in Lunaris turns to pure hatred after seeing him for the manipulative, power-crazed tyrant he truly is. Della wants to make Lunaris pay for all the lies he told her and using her for his own selfish motives.
A painting of Della
A picture of Della shoving her brother's face in cake
Dewey finds his mother in the rest of painting picture with Donald and Scrooge
Della with her brother, uncle, and unhatched sons
Della reading the map to discover where else to explore
Della arguing with her brother after he refused to do her request to come with her to the moon due her sons almost here to hatch.
Della sneaking into the Spear of Selene unknowingly sparking events that will change the Duck and McDuck families forever.
Della determined to reach the moon before the storm approaches her.
Della shown in the orb with Selene
Della is alive and surprise as she sees her family and her sons are grown up now.