The alien autopsy that supposedly took place in Roswell in the fifties was real but the aliens were not from outer space. They lived below the earths crust. About a million or so years ago, our ancestors lived in caves. some decided to leave the caves and live somewhere else. Others went deeper and deeper into the caves and evolved into a different kind of human. Years and years go by and they learn to harness the power of the earth's core.
As time goes by their population soars and they start hollowing out massive sections of the earth. This is felt on the surface as an earthquake. There was a huge eartquake somewhere in the fifties (probably) and down below the earth a double decker bus appeared one day. The fatties (I fuckin well discovered them so I can call them what I damn well please) decide to investigate and they think they have found aliens on the planets surface. They are so shocked and astounded to see people living on the surface (the fatties are highly evolved) and one of them crashes his flying saucer and ends up on the slab.
Go on, prove me wrong.