Walt Disney Productions filmed a successful sequel in 1976 called The Shaggy D.A. which starred Dean Jones, Tim Conway, and Suzanne Pleshette. It was followed by a 1987 TV-movie sequel, a 1994 TV-movie remake and a 2006 theatrical remake (see legacy section below). A colorized version of the film can be found on the 1997 VHS.
Wilby Daniels is constantly misunderstood by his father, Wilson. Wilson thinks Wilby is crazy half the time because of his elder son's often dangerous inventions. As a retired mailman who often ran afoul of canines, he has a hatred of dogs, and he can't understand why his younger son, Moochie wants a dog so badly.
Wilby and his self-centered rival, Buzz Miller, are constantly vying for the attention of girls while ignoring their friend Allison, who has trying to get one of them to notice her. Wilson notices that a man named Dr. Mikhail Valasky has rented a house in the neighborhood. When he sees Dr. Valasky has a stepdaughter about Wilby's age, Wilson tells Wilby to welcome Dr. Andrassy to the neighborhood in an effort to bring him and Dr. Valasky's daughter together. Although Wilby gets along well with the articulate and attractive French girl, named Francesca, she has also caught the attention of Buzz as well.
Buzz and Wilby take Francesca to the museum, where Wilby gets separated from the other two, who leave without him. Wilby ends up in a new wing, where he encounters Professor Plumcutt (whose newspaper Wilby used to deliver), who tells him all about mystical ancient beliefs, including the legend of the Borgia family, who used shape-shifting as a weapon against their enemies.
On the way out, Wilby collides with a table of rings, ending up with one in the cuff of his pants which he finds later. It is the cursed Borgia Ring, and when he reads the inscription on it, he turns into Chiffon, Francesca's shaggy Bratislavian sheepdog. Confused about what has happened, Wilby as a dog goes to Professor Plumcutt, who says he has invoked the Borgia curse upon himself, which can only be broken through a heroic act of selflessness. Wilby sneaks back home and falls asleep in Moochie's room. When Moochie wakes up the next morning, he is impressed to have a talking dog, but Wilby says he does not want to be a dog forever and needs Moochie's help in breaking the curse. After getting chased out of his own house by Wilson (who hasn't realized the dog is actually Wilby), Wilby has a series of misadventures, as he constantly switches back and forth between human and dog forms. Only Moochie and Professor Plumcutt know his true identity when he is a dog, as Wilby has spoken to them both in dog form. Finally, he goes to a local dance (as a human) and while dancing turns into a dog. He runs out quickly, and goes home.
The next day, Wilby (as a dog) and Moochie are talking when Franceska's butler Stefano comes out and drags Wilby into the house under the impression Chiffon ran outdoors. Stefano and Dr. Valasky (Franceska's adoptive father), discuss plans to steal a government secret, and Wilby overhears, as well as Dr. Valasky's desire to eliminate his own stepdaughter as he did her mother. Unfortunately, Wilby finds himself transforming again. As the dog he slips away unnoticed, but he has fully transformed into a human when the spies find him.
The spies capture him and force Franceska to leave with them, leaving Wilby (human) bound and gagged in the closet. Moochie sneaks into the house after Dr. Valasky, Stefano and an unwilling Franceska leave. Wilby once again becomes a dog, which frees him from the ropes, but he is not free until Moochie gets him out of the closet and the Valasky house. Wilby reveals the secret to his dumbfounded father, who is in disbelief until Moochie says Wilby is a dog and Dr. Valasky is a spy. Wilson goes to the authorities, who think he is a spy when he says Dr. Valasky attempts to breach Section 32, a restricted area, but first send him to Dr. J.W. Galvin, a psychiatrist, when he claims his son is a dog.
When Buzz appears at the Valasky residence to take Franceska on a date, Wilby (as a dog) steals Buzz's hot rod. Buzz reports this to Officers Hansen and Kelly, who are in disbelief until they see a dog driving the hot rod. Officer Hansen radios into headquarters that he is pursuing a stolen car, who treat it as routine until Hansen reports the suspect as a shaggy dog. The chief orders another squad car to apprehend Hansen and Kelly, however when Hansen and Kelly succeed at recapturing Buzz's hot rod, Wilby steals their squad car. When the other squad car sees a shaggy dog driving Hansen and Kelly's squad car, they dumbfoundedly realize it must be true and agree to aid Hansen and Kelly. Meanwhile, Buzz and Moochie browbeat Wilson into following the police, who in turn are following Wilby. However, Wilby has inadveratedly frightened Dr. Andrassy, who sees his car is being pursued by a squad car with lights on, and orders an alternate escape by sea to his boat at the marina.
The spies attempt to leave via boat, but the police call in the harbor patrol to apprehend Dr. Valasky and stop his boat. Wilby (dog form) swims up and wrestles with the men, as Franceska gets knocked out of the boat. Wilby forgets the fight and jumps overboard to swim Franceska to shore, where Buzz is waiting. The final transformation occurs when a net drops over Buzz and Chiffon, who growls at Buzz. Wilby suddenly reverts to human form, shouting at Buzz, who is dumbfounded that Wilby suddenly appeared out of nowhere. They suddenly realize that Franceska to fawning over Chiffon, whom she thinks saved her when it was actually Wilby. However, when Wilby sees he and Chiffon are in the same place at once, he realizes he broke the Borgia curse by saving Franceska.
Wilson and Chiffon are declared heroes, Franceska leaves for Paris without her evil adoptive father and former butler (both of whom have been arrested for espionage; and she gives Chiffon to the Daniels family for them to keep as thanks. Since Wilson has gotten such commendation for foiling a spy ring due to "his love of dogs", he can no longer have his dog-hating attitude, and allows Moochie to care for Chiffon as he wanted a dog all along. Wilby starts dating Allison, and resumes his friendship with Buzz, who has matured and stops his rivaley with Wilby over girls. Buzz remarks that it was foolish of them to fight over Franceska and is glad that she let Wilby have Chiffon.
In the late 1950s, the idea of an adult human turning into a beast was nothing new, but the idea of a teenager doing just that in a movie was considered avant-garde and even shocking in 1957 when AIP released their horror film, I Was a Teenage Werewolf, one of the studio's biggest hits. The Shaggy Dog betrays its successful forebear with Fred MacMurray's classic bit of dialogue: "Don’t be ridiculous — my son isn’t any werewolf! He’s just a big, baggy, stupid-looking, shaggy dog!"
The movie was originally intended as the pilot for a never-made TV series and advertised as "the funniest shaggy dog story ever told," although it is not in fact a story of that genre. The director was Charles Barton, who also directed Spin and Marty for The Mickey Mouse Club. Veteran screenwriter Lillie Hayward also worked on the Spin and Marty serials, which featured several of the same young actors as The Shaggy Dog.
Veteran Disney voice actor Paul Frees had a rare on-screen appearance in the film – for which he received no on-screen credit – as Dr. J.W. Galvin, a psychiatrist who examines Wilson (MacMurray). Frees also did his usual voice acting by also playing the part of the narrator who informs the audience that Wilson is a "man noted for the fact he hates dogs."
- Fred MacMurray as Wilson Daniels
- Jean Hagen as Frida Daniels
- Tommy Kirk as Wilby Daniels
- Annette Funicello as Allison D'Allessio
- Tim Considine as Buzz Miller
- Kevin Corcoran as Moochie Daniels
- Cecil Kellaway as Professor Plumcutt
- Alexander Scourby as Dr. Mikhail Valasky
- Roberta Shore as Franceska Andrassy
- James Westerfield as Officer Hanson
- Strother Martin as Thurm
- Forrest Lewis as Officer Kelly
- Ned Wever as E.P. Hackett
- Gordon Jones as Scanlon
- Jacques Aubuchon as Stefano
- Paul Frees as opening narrator/Dr. J.W. Galvin
- Jack Albertson as a reporter (uncredited)
While the movie itself is based on Salten's The Hound of Florence, a novelization of the movie published by Scholastic eight years later in 1967 made some interesting changes to the plot. First, Funicello's character Allison was removed entirely, and her name is not listed among the movie's principal performers. As a result, the rivalry between Wilby and Buzz is greatly reduced. Also, Dr. Valasky is changed into Franceska's uncle, not her adoptive father.
The Shaggy Dog had been at that point the most profitable film produced by Walt Disney Productions and heavily influenced the studio's live-action film production for the next two decades. Using a formula of placing supernatural and/or fantastical forces within everyday mid-twentieth century American life, the studio was able to create a long series of "gimmick comedies" (a term coined by Disney historian and film critic Leonard Maltin) with enough action to keep children entertained with a touch of light satire to engage their adult chaperones. Using television actors on their summer hiatus who were familiar to audiences but did not necessarily have enough clout to receive over-the-title billing (or a large fee) from another major studio was one way these comedies were produced inexpensively; they also tended to use the same sets from the Disney backlot repeatedly. This allowed Walt Disney Productions a low-risk scenario for production, any of these films could easily make back their investment just from moderate matinee attendance in neighborhood theatres, and they could also be packaged on the successful Disney anthology television series The Wonderful World of Disney (some of these films were expressly structured for this purpose).
Occasionally Walt Disney Productions would find one of these inexpensive comedies would become a runaway success and place at or near the top of the box office for their respective release year (The Absent-Minded Professor, The Love Bug). The initial release of The Shaggy Dog grossed more than $9 million on a budget of less than $1 million – an almost unprecedented return on a film investment, making it more profitable than Ben-Hur, released the same year. The Shaggy Dog also performed very strongly on a 1967 re-release.
- The film was followed in 1976 with a theatrical sequel, The Shaggy D.A., starring Dean Jones as a 45-year-old Wilby Daniels.
- In 1987, a two-part television movie set somewhere in the 17 years between the events portrayed in The Shaggy Dog and The Shaggy D.A., entitled The Return of the Shaggy Dog, presented a post-Saturday Night Live Gary Kroeger as a 30-something Wilby Daniels.
- In 1994, the first remake of the film was a television movie, with Disney regular Scott Weinger as a teenaged Wilbert 'Wilby' Joseph Daniels, and Ed Begley, Jr. playing a part similar to the one originated by Fred MacMurray in 1959.
- In 2006, Disney released a remake of the movie with Tim Allen as a 50-something Dave Douglas. This film has an entirely different story, characters, and transformation plot device unrelated to the original trilogy. To tie-in with the theatrical release of the 2006 remake, the original 1959 movie was re-issued in the USA as a special DVD labeled "The Wild & Woolly Edition," which featured the movie in two forms: one in the original black and white, the other a colorized version. In this DVD, while the original B&W version has been restored from its original negatives, the colorized version is left unrestored. In the UK, however, the 1959 movie has only ever been made available on Disney DVD in black and white.