Museum

I once worked in an art museum.
One day I made a plaque that read Marcel Duchamp and affixed it to the wall
next to the fire extinguisher.
Later I swapped an original Picasso with a poster of one in the gift shop.
No one noticed.
Finally, I set the Picasso poster on fire but nobody would put it out because
nobody wanted to risk the Duchamp.
This, of course, finally got me fired.
The next day, I went into the gift shop and bought the Picasso.
So now I have an original Picasso, but no one believes it's real.