If I learned everyone else on the planet was an alien, my day would probably go something like this. I would probably not be able to go to sleep because of what I just learned, so I would be up all night. At some point I would probably have some sort of an existential crisis due to the fact that, as far as I know, I am one of if not The only humane left in existence. However, after I get over the initial shock of the news I do not think my life would change very much. Even though everyone I have ever known and loved would have turned out to be an alien, they are still the people I have grown up with and the people who have cared for me all my life.