User blog:DeltaSquad5/How would you react if aliens announced their presence to us?

My reason for asking this was from watching this video from Novemeber 1977, in which an apparent extraterrestrial called Vrillon of Ashtar Galactic Command took over a TV channel in Southern England. (The video has been subtitled)

If something like this happened on a worldwide scale with a similar message, how would you react?

(Here's another example from Man of Steel).