"The Immortal" Hulk Hogan transforming into "Hollywood" Hulk Hogan at Bash At The Beach 1996.
It was awesome because no one could imagine Hogan as a heel after his big Hulkamania run in the 80's and early 90's, and no one even considered the possibility of Hogan turning because they were too focused on it being another WWF guy jumping over, since Hall and Nash were jumping from WWF and even playing the role of pretending WWF invaders at first. Bret Hart was rumored because he was negotiating with WCW in 1996 in real life. HBK was rumored because he was part of the Kliq with Hall and Nash and many thought he honestly was jumping. They didn't realize it was the very guy who represented the image of WWF itself, Hulk Hogan, even though he'd been in WCW for two years at that point.
It also worked because fans of WWF saw Hogan as a real life traitor for jumping to WCW, and two years later, they saw Hall and Nash as the same thing. So it fit in a way to see all three guys form a villainous group together. It was also cool seeing a member of the Golden Age/Rock 'N Wrestling era of the WWF in the 80's teaming up with two of the main stars of the New Generation of the 90's, in a WCW ring. Hogan's promo was also very real - he talked about fans turning on him and booing him, which they did. He referred to the "organization up North" turning their back on him, which they kinda did with the Huckster skits, poking fun of Hogan's age and whatnot.
It was magical for a lot of reasons.