Buckaroo Banzai is caught with his trusted allies, the Hong Kong Cavaliers, in a battle to the death between evil red aliens and good black aliens from Planet 10. Led by demonic dictator John Whorfin, who has taken over the body of Italian scientist Dr. Emilio Lizardo, the aliens try to get the Overthruster back from Buckaroo Banzai. But the good black aliens are willing to destroy Earth rather than let these renegades return to their planet.
Traveling back in time isn’t simple, as James Cole (Bruce Willis) learns the hard way. Imprisoned in the 2030s, James is recruited for a mission that will send him back to the 1990s. Once there, he’s supposed to gather information about a nascent plague that’s about to exterminate the vast majority of the world’s population. But, aside from the manic Jeffrey (Brad Pitt), he gets little in the way of cooperation, not least from medical gatekeepers like Dr. Kathryn Railly (Madeleine Stowe).
When the evil Skeletor (Frank Langella) finds a mysterious power called the Cosmic Key, he becomes nearly invincible. However, courageous warrior He-Man (Dolph Lundgren) locates inventor Gwildor (Billy Barty), who created the Key and has another version of it. During a battle, one of the Keys is transported to Earth, where it is found by teenagers Julie (Courteney Cox) and Kevin (Robert Duncan McNeill). Now both He-Man and Skeletor’s forces arrive on Earth searching for the potent weapon.
In this final chapter, Marty McFly (Michael J. Fox) obtains a 70-year-old message from the time-traveling Dr. Emmett Brown (Christopher Lloyd), in which he informs Marty that he has retired to a small town in the Old West. Marty then finds out that the Doc was murdered shortly after sending the letter. In order to save his friend, Marty will have to travel back in time, disentangle a lovestruck Doc from a local schoolmarm, and repair the DeLorean — all while avoiding a posse of gunslingers.
Michael (John Stockwell) and his girlfriend Ellie (Danielle von Zerneck) break into a military junkyard to find a science project for Michael’s class. They instead discover a strange glowing orb that absorbs electricity. When the orb begins to blend past, present, and future, it’s up to Michael and Ellie to stop the orb and save mankind.
A Pacific aircraft carrier enters a time warp and finds itself transported from 1980 to 1941 – just before the attack on Pearl Harbor. The captain is forced to decide whether to strike at the approaching Japanese fleet and change the entire course of World War II.
Motorcycle racer Lyle Swann (Fred Ward) is cruising through the Mexican desert when he accidentally stumbles into a time-travel experiment and finds himself transported back to the Old West of the 1870s. There he encounters an attractive local woman (Belinda Bauer) and a gang of criminals led by Porter Reese (Peter Coyote). Lyle’s motorized bike is impressive in the past — until it runs out of gas. Now Lyle must rely on his wits to take care of business and return to his own time.
Ash is transported back to medieval days, where he is captured by the dreaded Lord Arthur. Aided by the deadly chainsaw that has become his only friend, Ash is sent on a perilous mission to recover the Book of the Dead, a powerful tome that gives its owner the power to summon an army of ghouls.