The character was created by Carl Barks. Although she went through changes over the years with her name and relations to Donald, she officially was established as Della Duck, twin sister to Donald by Don Rosa.
Despite the fact that Della was missing in action, she is an adventurous high-spirited, daring, and headstrong woman, who loves going on adventures with her family.
In many early adventures, she has been smart, kind, and compassionate to help her family and others out of trouble, making everyone around better. Although she is good-natured, Della is also mischievous and highly impulsive. She is referred to as a prankster in "The Secret(s) of Castle McDuck!", as she had a dark sense of humor.
However, it has been implied that her thrill-seeking attitude can blind her to the dangers and consequences of her actions. This apparent selfish impulsiveness is what led to her being manipulated by Bradford Buzzard into becoming lost in space, although in "The Most Dangerous Game...Night!", Scrooge reveals that Della did, in fact, have the ability to read a situation and perceive all the possible outcomes, and in "Last Christmas!", she was also far more family-oriented and less impulsive than previously implied. What young Donald perceived as thoughtless and reckless behavior on Della's part was actually a well thought out plan to bond with him while simultaneously attempting to get Scrooge the best Christmas gift ever.
In the episode, "What Ever Happened to Della Duck?!", Della shares the traits of being as temperamental and impatient as her brother up to a point where she quotes his catchphrase: "Aw, phooey," but in contrast to Donald, Della speaks more clearly. Also, after returning to Earth, when she first meets Launchpad and learns that he is a pilot as well, she displays a small act of hostility towards him, naively thinking Scrooge had replaced her with Launchpad after her disappearance. She also demonstrates a similar musical inclination, a sense of humor, love for adventure, and childish impulsiveness to Dewey, an enthusiasm for the Junior Woodchucks and a nerdy love of video games like Huey, and Louie's ability to read situations, perceive all possible outcomes and unintentionally cause trouble without understanding the consequences of their actions or the people they would hurt. Nonetheless, after witnessing how off-the-rails her children's antics could get, she works up the courage to show tough love in "Timephoon!" by grounding Louie after one of his schemes gets too crazy and nearly costs him his family.
Della Duck is a white anthropomorphic duck with shoulder-length hair and swoop-bangs. She has a yellow-orange bill, legs, and feet. She is known to wear a brown flight jacket, a sea-green shirt, tan shorts, a brown flight helmet, black goggles, and a light blue scarf.
When she appears in the present day when she was stranded on the Moon, her hair is long, and part of her jacket and shorts had been torn, leaving her right arm bare, save for bandages around her forearm and a fingerless glove on her right hand. She has a bionic left leg, after her original leg was crushed by the wreckage from the Spear of Selene's crash, and was forced to amputate it somewhere above the knee to avoid being crushed by collapsing debris.
Swordsmanship: Della has also proven to be skilled in a fight, as she is handy with a sword and other tools.
Genius-level intellect: Additionally, Della is pretty good at building machinery, as she built her own bionic leg, and learned rocket science from a manual to rebuild the Spear of Selene over the course of five years. Also, Scrooge has stated in "The Most Dangerous Game...Night!" that Della was very good at figuring out shortcuts and calculating plans in their adventures. However, she isn't always the sharpest as she thought she could jump back to Earth from the Moon. Also, after returning to Earth, when she first met Launchpad and learned that he was a pilot as well, she naively thought that Scrooge had replaced her with Launchpad after her disappearance and displayed slight hostility towards him before leaving to confront her uncle. In "GlomTales!" she made a hard security system to keep Louie in his room during his punishment.
Piloting: Della also has skills as a pilot, as she flew planes and somewhat flew a rocket-like an astronaut.
Engineering: Della was able to create a fully functional prosthetic leg after she lost her real foot in her crash on the moon. She was also able to rebuild the Spear of Selene successfully before the Moon Mite dissolved her base and made it collapse. She also helped Launchpad rebuild the Sunchaser/Cloudslayer in "The Golden Armory of Cornelius Coot!"
Survival skills: Della gained experience in surviving alone in uninhabitable areas such as the moon when she was lost for over a decade, as in the episode "What Ever Happened to Della Duck?!"
Junior Woodchuck Knowledge: Like her eldest son, Huey, Della was a Junior Woodchuck herself, even bringing the guidebook to space. Later, in "Challenge of the Senior Junior Woodchucks!", she supports Huey in her Junior Woodchuck outfit before getting thrust into an adventure with her Uncle Scrooge.
Indomitable Will: Della is a very driven and determined individual, as well as virtually fearless in the face of death and danger. She survived on the moon with the oxygen gum, and wanting to see her kids made her more driven to succeed.
You won't stop me from getting home to my kids, you creepy crawly. I will not fail them again.
-Della yells in desperate anger at Moon Mite
Wait, the mite isn't a monster. It's a mother. [...] The mite isn't our enemy, it's just trying to survive. [...] Because a mother would do anything for the sake of her kids.
-Della realized that Moon Mite is also mother
Let me try something. I used to sing this old song to my boys before they hatched. "Look to the stars, my darling baby boys, Life is strange and vast, filled with wonders and joys. Face each new sun with eyes clear and true, Unafraid of the unknown, because I face it all with you."
'Sup, party people! I'm back in the hizou- Oh, no. Knew it was wrong as soon as I said it. Sorry, that was terrible. Can I get a do-over? Hi Uncle Scrooge.
-Della introducing herself to her family for the first time.
Wait, Huey, Dewey, and Louie? No, no, no...their names were supposed to be Jet, Turbo, and Rebel...I told Donald. I wrote it down in case no one could understand him.
-Della annoyed & frustrated at Donald for giving her sons different names instead of the ones she had in mind.
Boys, I don't know what to say except I'm so sorry for ever stepping foot on that rocket, I never meant to leave you or miss your first steps or potty-training.... Wait, you are potty-trained, right? What I'm trying to say is... for a decade, I fought every day to get back to this family and I will fight every day to be a part of it, if you'll have me?
-Della apologizing to her kids
I missed you so much. You deserve to have the best mom and I'm going to be the best mom, starting right now.
-Della deciding to be the best mom
Huey, Dewey, Louie, I know you're not used to having a mom and I am not used to being one, but I'll figure it out as we go along in time.
But you did accomplish something. You made it farther than anyone else has. You don't have to be me. You just have to be Webby. And you have your own way of doing things that is unique, and special. You don't have to prove yourself to anyone, and oh boy; I should really apologize to Launchpad.
-Della comforting a devastated Webby and realizing that she herself should apologize to Launchpad
Oh yeah. In the cruel void of space, it's easy to lose track of time. So one morning, I decided to have a staring contest in the mirror, but I was so desperate for human connection it lasted three weeks. To this day, I can't look in a mirror because I'm afraid I'll see "her".
You met Penny on the moon? Is she okay? I miss her constantly trying to impale me.
-Della learning that Donald met Penumbra on the moon
What?!? (laughing holistically) You must be deleterious from hunger! Here have some delicious Oxey... Chew... Oh no. No, no, no. This is the moon all over again!
-Della briefly loses her mind then regains it when she realizes she is in the same predicament when she was on the moon
Louie: You know when I'm terrified, which is often, I try to remember this old song. "Face each new sun with eyes clear and true, Unafraid of the unknown..." Della: "...Because I face it all with you." I wrote that song before I got lost. How did you hear it? Louie: Well, Uncle Donald used to sing it to us when we were little.
-Louie comforting Della by singing her lullaby
Louie: Well, we survived that. So what do we do now? Della: I don't know, but we'll do it together.
-Della promising Louie they'll do more adventures together.
Della has the least number of appearances of all the nine protagonists of the series: Scrooge, The Boys, Webby, Donald, Beakley, Launchpad, and herself.
This version of Della is very different than her appearance in comic series. She had blonde hair, had a bottom in form of a ruffled skirt and wore no pants like her brother and other family relatives as well as other anthropomorphic ducks including Daisy.
Della was occasionally referred to as Dumbella Duck, before Don Rosa's "The Life and Times of Scrooge McDuck" established Della Duck as her one official name. However, in the episode "Last Christmas!", when she and Donald were young, it was revealed that the name Dumbella was just a name Donald used to tease her. She is also occasionally referred to as Thelma Duck, however, this alternate name has not been acknowledged in the series.
Della is the second known character in the series to have a physical disability due to the loss of her left leg, with the first being Black Heron having lost her right arm.
Della's Lullaby was written to the tune of the Moon Stage Theme that is in the DuckTales video game.
Della never mentioned a husband in the series. Since he was never around in his sons' lives, Donald had to raise them in Della's eleven-year absence.
In "The Lost Harp of Mervana!", Della is scared and disgusted by fish, to the point of barfing when she says something related to fish or fish anatomy.
In "The Richest Duck in the World!", Della claims to have eisoptrophobia, fear of one's own reflection, a result of how she was so desperate for companionship during her eleven-year ordeal, she started talking to her reflection in a mirror and started to believe it was a real person.
Della's appearances within each season gradually increased over time. In Season 1, she only amassed a single appearance that didn't involve a photo nor flashback, in Season 2, her status grew to a recurring character after her return to Earth, and in Season 3 she was officially branded as a main character.
Her position as a newly-main character also gave her a spot on the intro for Season 3.