- “Thanks for the adventure. Now go have a new one!”
- ―Ellie's message to Carl, in her adventure book
Ellie first met Carl as a child when he wandered into her clubhouse. The two became close friends after realizing they shared a similar admiration for explorer Charles Muntz (who later in the movie becomes the main antagonist). Ellie made promises with Carl by saying "Cross your heart!" and Carl does.
Eventually, Carl and Ellie were married, but were unable to have children. They constantly tried to arrange a trip to Paradise Falls, but every time something always happened to prevent it. After Carl finally managed to acquire a ticket, Ellie died of old age and an unknown illness.
As a kid, Ellie had red hair with a bow. She had big teeth with a gap, and she wore overalls.
As Ellie grew older, she has gray hair and wore glasses, and she had footwear.
- Ellie has full speaking lines during her childhood years, but has no dialogue in her depicted adult years.
- Ellie's name is based on her voice actress, Elie Docter, Pete Docter's daughter.
- In Toy Story 3, a signature of Carl and Ellie Fredricksen was seen on a postcard in Andy's room.
- Ellie has her own musical theme composed by Michael Giacchino that's first heard when she and Carl meet as children and plays several times throughout Up after her death, particularly when Carl gets the house up in the air with the balloons and during the climactic battle between Carl and Muntz as it plays against Muntz's theme.
- Ellie is the sixth Pixar character to die, after Combat Carl, Hopper, Coral, Syndrome and GO-4.
- The balloon with a stick, which is the same one that Carl got, resembles the balloon (nicknamed "Balloon") from the Winnie the Pooh franchise.