- Marty McFly: "You built a time machine... out of a Yugo?"
- Marcus Irving: "It's a sensibly priced car. And it doesn't quite travel through time. Yet."
- — Marty McFly and Marcus Irving during their first meeting
The Yugo time machine was Doctor Marcus Irving's invention, a time machine comprised of a Yugo GX automobile that had to reach 88 miles per hour in order to time travel. It was uncompleted until 1986, when Irving stole Doctor Emmett Brown's flux capacitor, which allowed it to successfully travel through time.
During the Cuban Missile Crisis, General Groves and Colonel Lomax sought out Doc Brown, a scientist who had impressed Groves during his time on the Manhattan Project. Groves had thought that if anyone could invent time travel, he could.
However, upon arriving at the Brown Mansion on October 24, 1962, the pair had discovered that it had burned down on August 1st. Goldie Wilson let them know that most people in Hill Valley considered him an insurance thief.
They did not want to associate with a thief, so after the Cuban Missile Crisis had ended, General Groves and Colonel Lomax sought out another scientist to research time travel. Marcus Irving was given a lab and government funding to try to develop the necessary technology.
In January 1986, the United States government terminated the funding of Marcus Irving's time travel research, as his time machine wasn't complete since the final step had eluded him for the past 24 years. When trying to learn more about the government's research into time travel, Irving discovered that he had not been their first choice for building a time machine. Irving became jealous of Doc Brown being their first choice, and also angry at Brown for denying the offer and causing him to waste 24 years of his life. Thus, Irving set out to gather information on Brown.
Upon reaching Doc Brown's lab at 1646 John F. Kennedy Drive, he discovered it to be deserted. He conducted more research and learned of a close friend and assistant of Brown's, Marty McFly. Hoping to find out just how much success Brown had had with time travel, Irving went to Marty's house, only to see Emmett Brown in the DeLorean time machine reach temporal displacement, at the moment Doc left the canisters with Marty and his girlfriend Jennifer Parker.
At this point, Irving decided to try and contact Brown, leaving a message in Brown's second laboratory. On April 14, 1986, he came face-to-face with Marty McFly, who was also looking for Doc in an attempt to find out why his memories did not reflect the current timeline. He informed Marty that he had built a partially working time machine using a Yugo, and warned him that his conflicting memories could mean he could be erased once the current timeline caught up with itself.
Marty sent a message to Doc, who arrived shortly afterward. While Doc and Marty were talking, Marcus secretly removed the tires from the DeLorean, and used Doc's flux capacitor to solve his problem with flux energy, which was the final step needed for time travel.
He was afraid of altering time too much, so he had spent years driving around with the flux capacitor in his trunk, worrying that someone might steal it from him. Eventually, he decided to travel into the future to make himself rich. Since he was afraid of altering time too much, he decided to only time travel in "baby steps", so he could better prevent any major changes to the timeline. He decided to take 2008 technology back to 1997 in order to make himself rich.
By this point, he had upgraded his Yugo with steel panels to help with the dispersal of flux energy. He also upgraded the tires, as the polymers used in 1980s rubber tires aren't suited for the rigors of the space-time continuum. Once he began his plan, he realized that he could be confronted by Marty and Doc at any time, as unlike himself, they were time cowboys who weren't afraid to travel many years into the past and future, making large changes to the time stream.
Irving searched the internet for pictures of Marty and Doc from the 1980s. He then used those pictures to build several doppelgangers using futuristic parts and sent them back to 1986. Several of the Marty doppelgangers appeared soon after Irving had stolen the flux capacitor and kidnapped Marty. They tried to kidnap Doc as well, but he escaped in the DeLorean. It was still able to fly despite lacking tires, since the hover technology in the rims were untouched. One of Marty's doppelgangers held onto the DeLorean while it was in the air. This surprised Doc, as he thought that it would be very unlikely that Marty could have survived such a trip.
After fighting, Doc discovered that it was an android version of Marty, with a metal skeleton and lifelike skin and eyes. When the android was kicked out of the car, Doc returned to Marty to let him know that the situation was not as it appeared. He incapacitated the other android with the stun gun that Griff Tannen had used on him in 2035. They then went to find the remaining android before it could do any harm, but they were too late.
The android knocked out Needles' gang with a knock out serum mixed with a memory clouding agent that made their memory hazy. It was doing the same to Needles himself, when Marty showed up to stop it. Doc meanwhile, headed to the DeLorean, and found that Irving had repaired it, placing the flux capacitor back in place and replacing the tires.
Doc was going to use a remote control override on the android when the aged Marcus Irving used the knock out serum on him. He left Marty and Doc stranded on January 8, 19654 B.C. Doc feigned haziness from the serum, which really didn't affect him since the majority was used on Needles and his gang. This allowed him to lay a trap. Doc knew that Marcus would be afraid of major changes to the timestream. So, he told him, using slurred speech, that their existence in this era might wreck the entire ecosystem.
They then jumped into the river to escape sabre-tooth tigers. Marty barely made it, getting scratched in the face. They climbed a rock, which Doc knew was still solid in 1986, and waited for Irving. As Doc had predicted, he was worried about the butterfly effect that they might cause, so he showed up in his Yugo shortly after they arrived on the rock.
Once Marty and Doc were in the Yugo time machine, one of the androids healed Marty's scratch and they traveled forward to 1997. They were taken to Marcus Irving's lab where he locked them in a room with his androids, telling Marty and Doc that he didn't mind if they were killed in this time period.
Doc used his remote control override, and the DeLorean drove over an android, out of the garage, and up to the penthouse level, where Doc and Marty were being kept, crashing through the window.
The elevator Marcus was on automatically takes Marcus down to the garage level, while Marcus is pushing the button trying to get it to go up. Doc and Marty get into the DeLorean and fly down to the garage.
Doc explains that they can't just go back and stop Marcus from taking the flux capacitor, since the effects on a time traveler aren't instant, pointing out that it took a week for Marty to begin to fade from existence in 1955. Marcus and Doc could get in a reverse time race, with each vehicle going further back in time to try to prevent the other from making changes.
Doc rams the DeLorean into the elevator cord, slowing Marcus down. Marty and Doc then look at all the future technology. Marty sees a photo album and realizes that Marcus had been alone all this time. A female android that has been built to be Marcus Irving's sister comes online, and Doc and Marty realize that Marcus has become a bit crazy during his decade of living all alone.
Marty realizes that his fear of being all alone is what drove him to find Marty in the first place. They decide to take Marcus to his younger self, traveling in the DeLorean back to 1986.
In 1986, Marcus Irving is traveling in his Yugo GX, happy that he has taken the flux capacitor. Marty and Doc arrive from 1997 in the DeLorean, followed by the older Marcus in the Yugo.
Marcus is happy at first that his older self has come back to stop Marty and Doc, until he realizes how imposing he has become. He sees the army of Doc and Marty androids and thinks that everything he told Marty about alternate dimensions was true. However, Marty tells him the truth: that he has become a lunatic, a kidnapper, and a thief.
A woman and her niece get caught in the middle of the ensuing chaos, as the androids are ready to destroy everyone around them. Marcus realizes that he has become a person that he no longer viewed as himself, as his older self is willing to commit murder.
Marcus slams the flux capacitor into the android that is about to attack the innocent bystanders. The older Marcus Irving realizes he was almost a murderer. As he fades from existence, he commented that he is happy for the man he once was, and the man he could become.
The androids and the steel plated Yugo time machine fade from existence, and Marcus tries to explain that he is a scientist and states that the androids that faded from existence were holograms.
The woman introduces herself as Gabriela Sanchez, and her niece as Maria. Gabriela thanks Marcus for saving her life, and asks Marty and Doc who they are. Marty and Doc reply that they are Marcus Irving's friends. Which Marcus replies that they are probably his best friends, who helped him in a moment of crisis.
Needles arrives, and tries to harass Marty, but he wrestles with the unbelievable, and hazy, memories that he has of Marty fighting another Marty without a face. In light of this, he decides to leave Marty alone for a change.
Later, Marty is telling the story of the events to Jennifer while she is at work at Marty is telling the story of the events to Jennifer while she is at work at Shanerburger. Marcus tells Doc and Marty not to embarrass him, since he is on a date with Gabriella.
Marty and Jennifer wonder what will happen to Marcus, and Doc comments that he hopes he returns the Yugo to the authorities as not everyone can be trusted with unlicensed nuclear reactors. Eventually, Doc finishes repairing the flux capacitor and travels back to 1893.