In the year 2176, a magnetic storm has degaussed all recorded history. Three time travelers, Adam-11 (David Cassidy), Chanel-6 (Olivia d'Abo), and Heinz-57 (Geoff Doyle), are sent to the founding of America to retrieve a copy of the Constitution so society can rebuild. Thanks to a glitch, they end up two centuries too late. With the help of teenage slackers Chris Johnson and Tommy Sears (Jeff and Steve McDonald of Redd Kross), the three set out to repair their machine and find a copy of the Constitution. Hindering their progress are science geek Rodney Snodgrass (Liam O'Brien), who wants to use them as his science fair project; Rodney's older brother Eddie Trojan (Leif Garrett), who wants to seduce Chanel-6; and two CIA agents who are on their tail.
The film claims to be the first ever '70s retro movie.
The Spirit of '76 features examples of:
- 555: Most of the phone numbers on Rodney's wall use this.
- Actor Allusion: When Adam-11 complains about being stuck in the '70s, he stares sadly at a The Partridge Family lunchbox.
- And Starring: ...and Leif Garrett as "Eddie Trojan," introducing Jeff McDonald and Steve McDonald of "Redd Kross," Liam O'Brien, Martin Von Haselberg and Brian Routh of "The Kipper Kids," with appearances by Barbara Bain, Julie Brown, Tommy Chong, Iron Eyes Cody, Devo, Don Novello, Carl Reiner, Rob Reiner, Moon Zappa.
- Creator Cameo: Lucas Reiner appears briefly as a fireworks salesman.
- Every Car Is a Pinto: Parodied, with a Pinto just missing getting hit in the midst of a car chase, but bursting into flame anyway.Tommy: Uh-oh. Is that the kind of car I think it is?
Adam-11: But it didn't even hit it.
Chris: Doesn't have to. Let's get out of here!
- Future Imperfect: A badly garbled understanding of history sets the plot in motion.
- Mickey Mousing: As Adam-11 parks his dune buggy, the background music slows and then stops.
- No New Fashions in the Future: At the start everyone is wearing drab grayish quasi-protective gear. After the time-travelers return home, a certain decade's fashions get revived, and then some..
- Prank Call: Rodney likes calling random people to ask, "Is your refrigerator running?"
- Ridiculous Future Inflation: The inside of the time machine is papered with bills because money is almost worthless in the future.
- Roadside Wave: Adam-11 and Chanel-6 do this to the CIA agents when the agents run up behind their dune buggy in a muddy alleyway.
- Scatterbrained Senior: Dr. Von Mobil, the one man old enough to remember what life was like before the magnetic storm, is barely capable of stringing a sentence together and confuses the Preamble to the Constitution with the Miranda Rights.
- Spies in a Van: The two CIA agents are first seen in a Custom Industrial Appliances van.
- The Stinger: There's a 54-second post-credits scene of Chris and Tommy explaining various kitchen items to Adam-11. "It's a spray paint can, but with cheese!" The scene ends when David Cassidy starts laughing.
- Streaking: A streaker blocks the way of two cops who are chasing the time travelers.
- Title In: "AMERICA 2176"
- Victoria's Secret Compartment: In one scene, Chanel-6 hides her communicator in her top.
- Waxing Lyrical: When Tommy and Chris are describing Grand Funk Railroad to the time travelers, Tommy says, "They, like, they come into your town, and help you party down." Heinz-57 enters the lyrics into his keyboard.