#1: The Montreal Screwjob
Never, has there been a bigger instance of breaking the fourth than the Montreal Screwjob. In case you've been living under a rock for the past 22 years, let me fill you in.
As Bret Hart was approaching the end of his contract, the Hitman's real-life beef with Shawn Michaels made things difficult. As they approached their WWF Title match, Hart did not want to lose the gold to HBK in Canada, and the plan was for Hart to retain, and vacate the gold the next night.
Instead, Vince McMahon ordered referee Earl Hebner to ring the bell when Michaels locked Hart in the Hitman's own sharpshooter. A shocking moment that changed wrestling forever, it will go down in history as the most infamous moment of fourth wall breaking, as Superstars knew to never cross the boss.