5. They Possess The Ability To Predict Things
There is an unwritten rule somewhere in the Hitchhikers Guide To Time Travel that betting in an alternate timeline is strictly forbidden. It is just terribly unfair to bet on something you already know is a certainty. One man who broke that rule was Biff Tannen, and he nearly tore a hole in space-time! Yet being from another period doesnt stop most time travellers from exhibiting their superior knowledge of current events in a most uncouth fashion. Some matter-of-factly predict minor events in rapid order to establish their presence ("man sneezes, coffee spilt, baby farts"), whilst others scream and yell predictions at our faces ("Get out of here, there is a bomb!"). But whatever happens, we are usually very slow to take them at their word, and even after theyve saved our bacon of four different occasions and told us who wins the World Series, only then are we willing to consider that there might be something different about them. Most likely to say: I have to tell you this...
CASE STUDIES: Source Code, Déjà vu