This slip-up occurs when Marty and Doc go back to 1955 to get the sports Almanac from Biff. They have just traveled through time, and they are hiding the DeLorean behind the sign for the future site of the Lyon Estates subdivision. As they are covering up the car and making their plans, Marty puts his bare hand on the icy car. The problem is that in the first movie, Marty tries to touch the icy car, and it's SO cold that he pulls his hand away in pain. Doc even comments on how the car freezes to well below zero during time travel. So, how can Marty bear to lean on the car for a few seconds in the second movie when it was painfully cold in the first?