Ali vs Inoki was awful and had rules which din't make any sense because it was supposed to be staged, with ali taking a dive to lead to a rematch which he'd win, but in the time leading up to the fight he decided he couldn't go through with it and so they made up some rules on the spot. Ali actually suffered blood clots in his leg from getting kicked over and over in the same place for 45 minutes.

The WWF used Tyson in 1998, he helped promote wrestlemania, which drew 740,000 buys. I don't think he's ever done any MMA, although there was talk of it at one point. He was rumoured to be fighting Bob Sapp, who is a faily poor fighter but is a massive celebrity in Japan, but it all fell through.