Cast of My Stepmother Is an Alien

Dan Aykroyd plays Steven Mills, a widowed scientist who unknowingly falls in love with an alien named Celeste.

Kim Basinger portrays Celeste Martin, an alien sent to Earth to understand human emotions, who ends up falling in love with Steven.

Jon Lovitz plays Ron Mills, Steven's quirky brother who suspects that something is off about Celeste.

Alyson Hannigan portrays Jessie Mills, Steven's curious daughter who forms a close bond with Celeste.

Joseph Maher plays the role of Lucas Budlong, Steven's colleague who becomes suspicious of Celeste's true identity.

Seth Green portrays Fred Glass, a teenager who befriends Jessie and gets caught up in the chaos caused by Celeste's arrival.

Ann Prentiss provides the voice for the Bag, a comedic alien entity that communicates with Celeste.

Wesley Mann plays Grady, a quirky character who assists Celeste in navigating human customs and behaviors.

Tony Jay portrays Council Chief, a senior member of Celeste's alien council who monitors her progress on Earth.

Peter Bromilow plays Second in Command, another member of the alien council who keeps a close watch on Celeste's mission.

Nina Henderson appears as the Cashier, a minor character encountered by Celeste during her experiences on Earth.

Harry Shearer provides the voice for Carl Sagan, a well-known scientist whose voice plays a role in the alien communication system.