The People's Republic of China is severing relations with all other nations. They have mastered the art of miniaturization, and have shrunk all their people to the height of 2 inches. The ambassador of China, Ah Fong (Pat Morita), announces during a press conference that the key to all knowledge can be found from twins.
Caleb Swain (Jerry Lewis) and his wife Letitia (Madeline Kahn) are called "the most beautiful of all the beautiful people" by the press. However, when Letitia gives birth to twins who are called "monsters", the family doctor, Dr. Frankenstein (John Abbott) informs the parents that the twins won't live more than a few months. The Swains decide to allow the twins to live their short life in a mansion staffed with servants, including Sylvester (Marty Feldman).
Fifteen years later, the twins (also played by Lewis and Kahn) are still alive. They have large heads and appear to be mentally retarded. Their parents, who have not seen them in all those years, receive a visit from the former Chinese ambassador who informs them that their children are geniuses who can solve the world's problems.
The parents, along with the US president (Jim Backus), pay the children a visit. They reveal themselves to be well-behaved and intelligent, explaining that they acted "stupid" around the servants because they were simply emulating them.
A series of tests reveal that there is a telepathic connection between the twins, and their intelligence is only functional when they are together. Furthermore, when their heads are touching they reach a level of intelligence that has never been surpassed.
Their parents, fearful that incest may be prevalent, separate the two. They become despondent without each other, and the Chinese ambassador appears again to tell them to seek each other out. Once united, a spaceship appears and reveals that they are really aliens who were sent to Earth to solve all of the planet's problems. However, their alien father (voice of Orson Welles) reveals that Earth cannot handle their intelligence and returns them to their home planet.
The film was loosely based on the novel Slapstick: Or Lonesome No More! by Kurt Vonnegut. Director Steven Paul had played Paul Ryan in the stage production of Vonnegut's Happy Birthday, Wanda June and reprised the role in Mark Robson's film adaptation. Paul's screenplay shifted away from the serious aspects of the novel and placed more emphasis on its humor, as well as excluding Vonnegut's view of groups as extended families "whose spiritual core is common decency", and the importance of courtesy, kindness and dignity. Vonnegut considered the novel to be his worst work.
Martial artist Peter Kwong made one of his earliest appearances in this film, playing an astronaut in a flying fortune cookie.
This film was released in Europe in 1982, but did not see a US release until March 1984. There are two different versions, the 1982 version running 84 minutes, and the 1984 version, which was released to cable television as Slapstick in the US, running 82 minutes. Lewis promoted the US release on the March 21, 1984 episode of The Tonight Show Starring Johnny Carson.
Gene Siskel and Roger Ebert panned the film in their show At the Movies. Siskel described it as "the single worst movie of 1984", saying it was shockingly bad, insensitive, cruel, boring, unfunny and cheaply made. He summed up by proposing that film encyclopedias "ought to have an entry called Bad Movie and the illustration ought to be a still photo from Slapstick of Another Kind... The best thing that could ever happen to this film is that it never be shown anywhere." Ebert concurred, describing the film as offensive, unsavory and painful.
In At Millennium's End: New Essays on the Work of Kurt Vonnegut, Kevin Alexander Boon said that the film "circumvents everything that is intelligent about Vonnegut's fiction" and that it is one of the worst adaptations of Vonnegut's work.
Leonard Maltin praised the performances of Jerry Lewis and Sam Fuller, but described the film as "appalling".
Lewis was nominated for the Golden Raspberry for Worst Actor for his role in this film.
Nathan Rabin, writing for The A.V. Club, called the film "a crass violation of everything Vonnegut stood for".