The Tyson Zone is a term coined by sports writer Bill Simmons. It refers to a mythical sphere that only a small number of celebrities are capable of reaching in our very minds. If a famous person is in the Tyson Zone, their public persona and behavior has become so erratic and bizarre that you are bound to believe, or at least be able to imagine any story you hear or read about them, no matter how outrageous and inconceivable it is.
The original definition from 2004, given by a fan, for which Bill Simmons created the name "Tyson Zone", goes as follows:
"if a friend said, 'Did you hear that (fill in celebrity's name) just (fill in the insane behavior: urinated on a police officer, began breeding unicorns, etc.)?' I would have no problem believing it was true."
The inspiration for the trope of course is ex-professional boxer and former undisputed heavyweight champion of the world Mike Tyson, whose escapades and instances of erratic behavior have become too numerous too mention - just internet search them to refresh your mind. Examples of other people who have commonly been referred to as having reached the Tyson Zone are Dennis Rodman, the late Michael Jackson, and, of course, Donald Trump.