"I hate alternate timelines. They make for messy bookkeeping."
— Squishydodo, Black-ops elf, Sluggy Freelance
Doc: Obviously, the time continuum has been disrupted creating this new temporal event sequence, resulting in this alternate reality.
Marty: English, Doc.
Doc: Here, here-here. Let me illustrate.
(He moves aside cardboard boxes to set up his chalkboard)
Doc: Imagine that this line represents time. 1985...the future...the past. Prior to this point in time, somewhere in the past, the timeline skewed into this tangient, creating an alternate 1985. Alternate to you, me, and Einstein, but reality for everyone else.
— Doc Brown and Marty, Back to the Future Part II