“So Doc, you’re telling me that my son from 2015 stole the Delorean and travelled further into the future to get his hands on a super-human serum.”
“Exactly, Marty! I foolishly left a holo-mag from 2185 lying in the passenger seat, blindly oblivious of the terrifying repercussions to the space-time continuum if anyone from the past were ever to see it. Obviously the “before” and “after” holo-ads were too enticing for the impressionable teen!”
“Then he travelled back in time and injected his 12-year-old self with the serum-”
“-stranding us here in 2015 where a hulked-out Marty McFly Jr has been ruling Hill Valley with his iron fists ever since he hit super-puberty!”
“Heavy. Does he hang around with Griff’s gang now?”
“From my digging at the archives, I’ve learned that Griff died 5 years ago after upsetting Marty Jr during a lunch break dispute.”
“A lunch break dispute?”
“My understanding is that Griff accidentally spilled some milk over Marty Jr’s new pants.”
“Oh. And what of the Delorean?”
“Marty Jr still has it, though I understand he’s had it ‘pimped out’ since we last saw it…”