Due to a glitch in the mundane/celestial time-space continuum, all three arrive at the Pearly Gates more or less simultaneously, even though their deaths have taken place decades apart.
The first to present himself to Saint Peter is Einstein.
Saint Peter questions him. "You look like Einstein, but you have NO idea the lengths certain people will go to, to sneak into Heaven under false pretenses. Can you prove who you really are?"
Einstein ponders for a few seconds and asks, "Could I have a blackboard and some chalk?"
Saint Peter complies with a snap of his fingers. The blackboard and chalk instantly appear. Einstein proceeds to describe with arcane mathematics and symbols his special theory of relativity.
Saint Peter is suitably impressed. "You really *are* Einstein! Welcome to heaven!"
The next to step up is Picasso. Once again Saint Peter asks for his credentials. Picasso doesn't hesitate. "Mind if I use that blackboard and chalk?"
Saint Peter says, "Sure, go ahead."
Picasso erases Einstein's scribbles and proceeds to sketch out a truly stunning mural... bulls, satyrs, nude women, etc. He captures their essences with but a few strokes of the chalk.
Saint Peter claps. "Surely you are the great artist you claim to be! Come on in!"
The last to present himself is George W. Bush. Saint Peter scratches his head. "Einstein and Picasso both managed to prove their identity. How can you prove yours?"
George W. looks bewildered, "Who are Einstein and Picasso?"
Saint Peter sighs... "Come on in, George."