"Just for fun, let's examine the premise as if we don't know who any of these characters are. A bunch of poorly dressed motherfuckers have a great big apocalyptic punch-up until only one survives, whereupon aliens invade, so said survivor travels back in time (no they don't say how, put your arm down!) and brings a warning to two rodeo clowns and a prostitute. Then he does a weird thing that bestows superpowers upon a whole bunch of random civies, his assumption perhaps being that if the entire world consists of poorly dressed motherfuckers having a punch-up then perhaps the aliens will just get freaked out and quietly leave."