I was on a business trip for work two years ago. On a plane from Washington, D.C. to Chicago, I gut bumped up to first class. Just as we were about to board, who should come on and take the seat right across from me, but Cassius Clay himself!
He seemed pretty nice. We were delayed taking off, so the flight attendants allowed Clay to walk back towards the coach section, where he performed a few small magic tricks for the passengers before it was time to take his seat again and we took off. He never really talked much during the flight though.
He became much more tolerable after the brain damage. He seemed to have shut up.