My Stepmother Is an Alien is a 1988 American science fiction comedy film directed by Richard Benjamin. It stars Dan Aykroyd, Kim Basinger, Jon Lovitz, and Alyson Hannigan. The film follows the story of Celeste, an extraterrestrial woman who is sent on a secret mission to Earth, after her home planet's gravity is mistakenly disrupted by Steven Mills, a widowed scientist raising his daughter Jessie as a single father. The film was the film debut of Juliette Lewis.

Plot

Steven Mills is a widowed scientist working on different ways to send radio waves into deep space. After he sends a radio wave out of the galaxy, it hits a planet (Cosine N to the 8th), causing a disruption of gravity on the planet. Celeste is sent to investigate who could have done it and how it was done, believing it was an attack. She is aided by a device called Bag: an alien tentacle with a single eye and a mind of its own disguised as a designer purse. Bag is able to create any object, such as diamonds and designer dresses, almost instantaneously. Celeste crashes a party hosted by Steven's brother, Ron, and immediately draws attention to herself by making outdated references to TV shows and political slogans under the mistaken belief that they are current (information that had actually taken 92 years to get from Earth to her home world).