A camera pans across the continent of Africa where the narrator describes how dark and terrifying it is, amid jungle sounds and roars. As the camera pans across the darkest area, we hear the melodious sound of someone singing. A second later the camera opens on a singing giraffe named Nelly, who is performing for her animal friends. A hunter appears from out of the bush, and exclaims, "I wouldn't have believed it if I hadn't heard it with me own eyes!" and immediately has her sign a contract offering her fame and fortune.
Nelly waves a tearful goodbye to her friends in the jungle as she leaves for civilization, captivated by the idea of show business. Once she arrives in New York City, she is put to work singing jingles for "Algonquin Rutabaga Tonic" - a cure for ailments, puts on live stage shows, and produces a line of giraffe-neck sweaters, effectively making turtleneck sweaters out of fashion.
Overtime, Nelly becomes lonely with fame and longs for male companionship. One day she wanders into the zoo and falls in love with a male giraffe, but she finds out he's already married (albeit unhappily, as the "wife" catches him looking at her). Scandal ensues and her agent begs her to break off the affair for the sake of her career. After a disastrous opera opening, rumors of her being a homewrecker, and her agent only able to get her roles in foreign films before ditching her entirely, Nelly returns to the zoo to be with the giraffe she flirted with, only to find him snuggling with his wife and wanting nothing to do with her. Devastated over her ruined career and reputation, Nelly returns to Africa to live out the rest of her life in obscurity.
As Nelly sings a beautiful love song, we see her sad reflection in a pond, tears dripping from her eyes, and from the eyes of her jungle friends. Moments later, another male giraffe begins singing along with her. The two fall in love and Nelly is finally happy.
- Nominated for an Academy Award in 1962, for Best Short Subject, Cartoons.
- Ed Prentiss, the narrator of this film, used to be "Captain Midnight" on radio in the 1940s.
- Ed Prentiss also narrated Chuck Jones' "Martian Through Georgia" a year later.
- Gloria Wood sang the original "Rice-A-Roni, The San Francisco Treat" TV jingle.
- Gloria Wood was also the vocalist for Kay Kayser's "The Woody Woodpecker Song" and was dubbed the singing voice of Marilyn Monroe, Vera Ellen, and Betty Grable.
- Nelly's Folly did not end with the familiar "That's all, folks!" title card, but rather, with a slide that read: "Merrie Melodies: A Warner Bros. Cartoon. A Vitaphone Release". These words appeared in purple, green, and blue, respectively, against a black background.
- "Auld Lang Syne"
- "The Flower of Gower Gulch", written by Michael Maltese
- "Voices of Spring", by Johann Strauss
- "Aloha Oe", by Queen Liliuokalani
- "Columbia, Gem of the Ocean", aka "The Red, White and Blue"
- "Then You'll Remember Me", from Balfe's opera "The Bohemian Girl"