#9 The debut of Y2J (1999)
It may be impossible for younger WWE fans, and youngsters in general to imagine, but the Y2K scare of the 90s was indeed very real. People imagined the worst, with computers crashing, servers being obliterated and even the world coming to an end because of the said bug.
Playing off this fear, WWE introduced WCW superstar Chris Jericho as Y2J, during a segment with the biggest star of the time, The Rock. A countdown clock was seen on television, leading up to the reveal.
WWE fans were enthusiastic and elated when they saw the Superstar jump from one camp to another. While Jericho has had a spectacular career since then, his debut is still remembered with fondness, to this day.
Bear in mind that this was during the Monday Night Wars, and the internet wasn't as big a thing as it is now. The surprise for most fans was indeed, quite genuine. The pop was indeed quite heartfelt.
How cool is to see that so many years later, Chris Jericho is still a big deal in the world of sports entertainment!