That one you can explain, but in doing so it just makes the whole thing a million times more confusing. Right, so the end of the first film confirms that two people can exist at the same time, but it's a bad idea for them to interact. That's why when Marty travels back to 1985 a few minutes before Doc gets shot by the Libyans, he has to make sure that his past self doesn't see him. That would cause a paradox, see? But that also implies that when this event first played out, there was also a Marty watching then. Else none of this would've happened. Which means that there are probably an infinite amount of Martys, travelling around time and narrowly avoiding each other. And each of those Martys probably affected the timeline in different ways. The crappy McFly home life seen at the start of the film could very well have been down to a different Marty tampering with things in the wrong way. For the film to work at all there always has to be a Marty that's back in 1955 messing with things, and one in the present, and another watching the one in the present go back in time, and so on. Not only does that bring up the infamous Grandfather paradox, but the implication that there's loads of Martys out there - cos there are two existing at once - that have to be dealt with. Two can't exist at once. So where does New Marty go?
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/
