#1 WrestleMania 13
Planned match affected: Shawn Michaels vs Bret "Hitman" Hart
WrestleMania 13 should have been the simplest event to book. With then WWE Champion Shawn Michaels having defeated Bret Hart to win gold at WrestleMania XII, the obvious headliner for the big show was Michaels returning the favor to the "Hitman."
However, back in 1997, Michaels didn't work like that. Completely unwilling to do business with Hart, who had recently signed a 20-year contract, for $1.5 million, double what champion Michaels was earning, it led to HBK developing an inferiority complex.
Michaels was further miffed when he learned that WWE Chairman Vince McMahon wanted him to drop the WWE Championship to Sycho Sid on Raw, prior to 'Mania.
The Hart bout would therefore be a non-title. Aghasting at the prospect of losing two major matches back-to-back, Michaels exaggerated a knee injury and advised McMahon that his in-ring career might be over.
Michaels therefore vacated the title, rather than losing it in the ring and had his WrestleMania match with Hart canceled.
Then, true to form, he returned to the in-ring competition, around six weeks after 'Mania' miraculously recovered.
With Michaels out of WrestleMania, Stone Cold Steve Austin was given the match with Hart instead and the pair contested one of the greatest matches of all time, in any company.
In an all-out war, the pair performed a double turn, with Hart going heel and Austin becoming the biggest babyface in wrestling history.
Michaels's exit from the Hart match in hindsight was probably the best thing to happen to WWE and Austin. Without that match, you could argue that Austin would not have become quite as big a superstar as he ultimately did.
You can't argue that what actually happened was therefore an upgrade on the original plans, even if the box office at the time was much lower than it would have been had Michaels competed.