The comet Kahooey is incoming, and thanks to Biff Tannen, Hill Valley is panicking about the arrival of aliens. When Doc becomes a scapegoat, Marty and the boys travel back to the 1960s to solve the problem.
This episode includes examples of the following tropes:
- Alien Abduction: To keep Biff from stirring everyone up and getting Doc in trouble, Marty and the boys pose as aliens, using the DeLorean as their spaceship, and pretend they want to take him with them. Biff begs to be released. After he promises to keep their visit a secret and not to accuse anyone, they let him go.
- And I'm the Queen of Sheba: When Doc introduces himself (while Marty and the boys still think he might be an alien), Marty sarcastically answers that he's Michael J. Fox. Doc doesn't know who he's talking about.
- Half-Human Hybrid: While they're still thinking Doc might be an alien, Jules and Verne gleefully talk about the possibilities inherent in their being half-alien.
- Mistaken for Aliens:
- Upon their arrival, Verne mistakes a hippie for an extraterrestrial.
- In the 1960s, Doc put together a pedal-propelled ship to get past the city lights and improve his view of the incoming comet. That, plus the magnetizing effects created by the ship and his alien-like cooling suit, cause Biff and even his sons and Marty to think he's actually from outer space.
- Mythology Gag: Marty sarcastically says that he's Michael J. Fox, his actor in the films. Verne admits that he can see the resemblance. This also subtly lampshades the fact that he is not Michael J. Fox in this series.
- Series Continuity Error: The Hill Valley clocktower is shown running in 1967. This contradicts the films, which made a plot point of the fact that the clock never ran again after 1955.
- We Come in Peace — Shoot to Kill: Once the Hill Valley military thinks the alien is holed up at the Browns' house, they surround it and threaten to blow the place to smithereens.
