The film stars Dennis Quaid, Martin Short, Meg Ryan, Robert Picardo, and Kevin McCarthy.

In San Francisco, down-on-his-luck U.S. Navy aviator Lt. Tuck Pendleton resigns his commission and volunteers for a secret miniaturization experiment.

They are transferred into a syringe to be injected into a rabbit, but the lab is attacked by a rival organization, led by scientist Dr. Margaret Canker, that plans to seize the experiment and steal the miniaturization technology.

In a last-ditch effort to stop the experiment from falling into the rivals' hands, the wounded Ozzie injects Tuck and the pod into an unsuspecting passerby - Jack Putter, a hypochondriac Safeway grocery clerk, who is exploited by his boss and belittled by Wendy, a superficial co-worker on whom he has a crush.

At the lab, the scientists explain to Tuck and Jack that the other group stole one of two computer chips that are vital to the process.

Jack contacts Tuck's estranged girlfriend, Lydia Maxwell, a reporter who has had dealings with the Cowboy.

After following him to a local nightclub, Lydia allows him to pick her up as Jack encounters Wendy, who, thinking he has been living a double life, shows an interest in him.

Once taken to the laboratory, the criminals shrink Igoe and inject him into Jack to locate Tuck, kill him, and obtain the other chip that is attached to the pod.

After Igoe has been injected, Jack and Lydia free themselves and order everyone in the laboratory, including Scrimshaw and Canker, into the miniaturization device at gunpoint.

Not knowing how to operate it, though, they accidentally and unknowingly shrink everyone to half their original size while trying to retrieve the chip.

Back at the lab, with only minutes of supplemental oxygen left in the pod, Jack follows Tuck's instructions to eject it from his lungs by making himself sneeze due to his hairspray allergy.

When they climb into the limousine, the Cowboy is shown to be the driver, and the shrunken Scrimshaw and Canker are hiding inside a suitcase in the trunk.

The film began as an original script by Chip Proser, who called it "basically a rip off of Fantastic Voyage.

"[3] According to Dante, Boam "approached it ... from the concept of what would happen if we shrank Dean Martin down and injected him inside Jerry Lewis.

So when Steven wanted to do it, Warners thought I was a God and any amount of money it would take to do the movie they would spend.

"[3] Quaid's role was originally envisioned to be played by an older actor, but then they decided to make the character younger.

The website's consensus reads: "A manic, overstuffed blend of sci-fi, comedy, and romance, Innerspace nonetheless charms, thanks to Martin Short's fine performance and the insistent zaniness of the plot.

"[13] Metacritic, which uses a weighted average, assigned the film a score of 66 out of 100, based on 15 critics, indicating "generally favorable" reviews.

[14] Roger Ebert of the Chicago Sun-Times gave the film 3 stars out of 4, stating "Here is an absurd, unwieldy, overplotted movie that nevertheless is entertaining - and some of the fun comes from the way the plot keeps laying it on".