Why is Biff at Marty's house at the end of BttF3

Cafe Society
1

Edit: Just to clarify, Marty time travels from 1885 and arrives back at 11:00 AM Sunday October 27, 1985. At the beginning of Back to the Future II (end of Back 1) it is Saturday morning. At the end of Back 3, it is Sunday morning/afternoon

Marty is wearing his wild west clothes and he goes up to the truck and Biff says “Hey get away from there, butthead” and then he realizes it is Marty and goes says “oh, sorry Marty, I didn’t recognize you in those clothes”

then Marty goes to his mom, and she is surprised to see him. She thinks he is still at the lake with Jennifer.

So, his family does not think he is there. And naturally, if he had gone to the lake, he would take his truck, so his family does not expect the truck to be there.

So why is Biff there working on it? Surely his family would not have called Biff over to work on a truck they don’t expect to be there. And he had just waxed the BMW yesterday, so he wouldn’t be working on that.

2

Why couldn’t they have taken Jennifer’s car to the lake?

3

Jennifer doesn’t have a car.

That’s why Marty was so upset when Biff crashed George’s car at the beginning of BttF1.

“I needed that car tomorrow night, dad”

4

The universe of BTTF1 has little relation to the universe of BTTF3. Thinking fourth dimensionally, that Jennifer could have a car.

Also, the truck is new to the original Marty of BTTF3 as well, so it’s possible it was always supposed to be in the garage as it wasn’t Marty’s yet.

5

Biff wouldn’t know if Marty had taken the car out or not. If it’s a regular Sunday Morning gig for Biff to wax Marty’s car, he shows up, it’s there as usual, then he waxes it. If it was out, he’d go home.

6

Yeah I’ve always had a problem with that.