Enforced Method Acting: The Montreal Screwjob, oddly enough. With Vince being caught on camera yelling at the ref to ring the bell, there was no way to pretend it didn't happen in kayfabe. Having made himself into a villain, Vince ran with it and created the "Mr. McMahon" character.
During his late 1998 angle with Mick Foley, Vince explicitly told Mick not to tell him what he was planning to do in their bits and that Vince would just react naturally to the stupidity. It led to some of the funniest bits ever on WWE programming.
At the 2005 Royal Rumble, he rushed to the ring to restart the main event after John Cena and Batista eliminated each other. In the process of entering the ring, he tore both his quads. He had to do his part sitting in a corner of the ring in excruciating pain.
Executive Meddling: For years, Vince has taken a direct and personal hand in WWF/E booking, with extremely mixed results. Sometimes the results are great, such as when he kept Vince Russo in check during the Monday Night Wars and turned the then-floundering WWF around. And then there are the results that don't work, like the whole Katie Vick angle.
Marth Debuted in Smash Bros.: Most people associate the "Mr. McMahon" character with him post-Montreal, but he actually played a sort of prototype of this character in a crossover with the United States Wrestling Associationnote Which featured long-time wrestler Jerry Lawler as its ace on USWA television.