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

[...]

- I have buried the DeLorean in the abandoned Delgado Mine adjacent to the old Boot Hill Cemetery as shown on the enclosed map.

- Hopefully, it should remain undisturbed, and preserved until you uncover it in 1955.

- Inside, you will find repair instructions.

- My 1955 counterpart... That's me... should have no problem repairing it, so that you can drive it back to the future.

- Once you have returned to 1985, destroy the time machine. Destroy it?

- Yeah. Well, it's a long story, Doc.

- Do not, I repeat, do not attempt to come back here to get me. I am perfectly happy living in the fresh air and wide-open spaces.

- 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.

- I know you will give him a good home. Remember to walk him twice a day, and that he only likes canned dog food.

[...]