- "Happy Trails, Marty!"
- —Doc, as Marty travels back to 1885
- "He [Marty] closed the [car] door again as Doc stepped out of his path. Marty put the DeLorean in gear and turned the car across the asphalt and gravel, toward the drive-in screen. / "Happy Trails, Marty!" Doc called after him. "Vaya con Dios!" / Marty waved and shifted the DeLorean up through the gears. He aimed the car for center screen and floored the accelerator. "
- —From Back to the Future Part III by Craig Shaw Gardner (quote, page 37)
"Happy Trails" was a film quote from Westerns, used by cowboys to wish each other a safe journey.
Behind the scenes
- In the novelization (see Quote above), after calling "Happy Trails, Marty!", Doc adds "Vaya con Dios!" which means "Go with God!" in Spanish.