One day there is a terrible accident with a tanker truck of nerve gas. It crashes near an insane asylum in California.
Everyone in the facility is rendered unconscious. When they wake up, everyone is naked and they all have amnesia.
No one can remember if they are a doctor or a patient, so they just put on whatever clothes they find and behave accordingly.
The most lucid of the inmates gets some paint and changes the sign out front to say "Sun Microsystems".