2015C was an ABC timeline. It was a version of 2015 created when old Biff Tannen stole the DeLorean time machine and traveled back to 1955 to give his younger self the Grays Sports Almanac, which in turn resulted in the creation of 1985A.
Marty McFly suggested to Emmett Brown in 1985A that they should travel back to 2015 and stop Biff from stealing the DeLorean in the first place. However, Doc pointed out that if they did so, it would only be the future of the current alternate timeline.
In the original timeline, George McFly was still alive. In 2015C, he is deceased.
Biff Tannen had deceased prior to 2015 in this timeline. Despite not existing in this timeline in 2015, the 2015B version of himself is still able to go back to 1955 and still exist there for the same reason Marty and Jennifer are able to leave 1985 to travel to a future 2015 where they still exist. The ripple effect began in 2015 and hasn't yet caught up to 1955.
Lorraine Baines McFly
Behind the scenes
- The 2015C timeline is visible in a deleted scene, with Biff being erased from existence after returning from an altered past, and the changes to the McFly home in Hilldale not visible to the viewers. The finished film only shows Biff suddenly clutching his chest in pain after he exits the DeLorean, causing the top of his cane to break off and fall inside the time machine, and staggering away before slumping to the ground behind a stationary car, where the scene ends. However, in the aforementioned deleted scene, this carried on to show Biff collapsing sideways and vanishing.
- 2015C is the third version of the timeline. In the original timeline, Marty Jr. robbed the Hill Valley Payroll Substation, Marlene McFly attempted to break him out, and both were sentenced to long prison terms. In the altered version, Griff Tannen and his gang were jailed, and the McFly kids did not commit those crimes. 2015C was returned to the second version when the almanac was burned. A fourth version of the timeline was created after Marty decided not to race against Douglas J. Needles, essentially making Marty and Jennifer's future yet to be written, and as blank as the CusCo "YOU'RE FIRED!!!" fax that faded away before the latter's eyes.
- Back to the Future Part II (deleted scene, rippling in just as Doc and Marty leave 2015, but not seen)