There are weird movies, and then there's Mars Attacks.
Martians come and may have intended to annihilate humans all along, or maybe that hippie just ruined everything with his peace-and-harmony dove. It's always the doves, man. The peace pigeons.
In the end, it doesn't matter what started it, because the Martians kill everyone in Congress and we go to war. It's comedy, folks! Because what else would it be when you have animated human heads - just the heads - or human heads transposed onto other animals because the Martians just want to see what happens, or Martians defacing our monuments while they blow up the world? However can humanity be saved?
Let's just say that the time has come to be grateful for Slim Whitman.