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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 finale, her hair grew much longer but was later cut back to normal after returning to earth.
Despite the fact she is missing in action, she is known as an adventurer. It has been shown that is a high-spirited, daring and courageous woman who loves 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 it's also she shown to be prankster, as shown in The Secret(s) of Castle McDuck!. However, her thrill-seeking personality often blinds her to the dangers and consequences of her rash selfish actions, which later resulted her becoming lost in space.
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.
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 one of the godesses
Della is alive and surprise as she sees her family and her sons are grown up now.