Yeah. Well, it's a long story, Doc.
3 seconds sound clip from the Back to the Future Part III movie soundboard.
You can hear this line at 00:08:50.998 in the DVD version of the movie.
Quote context
[...]
- Hopefully, it should remain undisturbed, and preserved until you uncover it in 1955.
- Inside, you will find repair instructions.
- Once you have returned to 1985, destroy the time machine. Destroy it?
- Yeah. Well, it's a long story, Doc.
- And I fear that unnecessary time travel only risks further disruption of the space-time continuum.
- And please take care of Einstein for me. Einstein?
- He's your dog, Doc. Einstein is what you call your dog in 1985.
- These are my wishes. Please respect them and follow them.
[...]