As far as taglines for demos go "When aliens attack, monsters fight back" is one we can get behind. I mean, that is true. Who could argue with that? Unless it's subtextual meaning is that society should release neo-nazis against new immigrants to the country who are taking our jobs, etc - in which case, we'd disagree with it a lot. Anyway, this is the demo of the game of the new Dreamworks film. You can download it from here, for about half a gig of Monster/Alien demonstration action - that is, three levels staring the leads (A sort of puzzle/platformy thing, a racing dodging thing and a fighter-thing). And here's a couple of videos...
That girl doesn't exactly look monstrous to me. Unless the subtext is that teenage girls are monsters, in which case... actually, I can get on side with that one.
(Except for Lucy. SHE WAS REALLY MEAN. :( :( :( )
I'll stop now.