Adrien Brody
Adrien Brody went off-script when he hosted SNL on May 10, 2003, after scrapping all the “good” ideas for sketches all week in the writer’s meetings. The Oscar winner did a skit where he donned dreadlocks and a pretty bad accent when portraying Jamaican performer Sean Paul.
Source: The Cheat Sheet
That performance drew dirty looks and resulted in a permanent ban from the show which was called by producer Lorne Michaels. I gotta say, it’s pretty shocking to hear, considering Brody is such a renowned actor.