-Undertaker's original name was to be Kane The Undertaker instead of just the Undertaker. He was introduced as such on an episode of Superstars of Wrestling but they dropped it to just The Undertaker a week later when he debuted at the 1990 Survivor Series. However, they later did an article on the Undertaker in an issue of WWF Magazine later that actually mentioned in passing about how the original Kane name was in reference/memorial to his deceased brother who had died in a fire several years before. Given that WWF never intended for Taker to have a physically/mentally disfigured-in-a-fire brother later on (no way did they plan on that several years in advance), it ended up being a very interesting piece of (unintended) continuity.
-The only two Wrestlemanias where Hulk Hogan lost by pinfall (WM 6 & 18) were both clean losses to babyfaces, and both events were held in the same stadium - the Skydome in Toronto, Ontario, Canada. Ultimate Warrior was the man who pinned him at WM6 and The Rock was the man who pinned him at WM18. Ironically, Warrior's name in the UWF (the place where he first gained a small bit of notoriety before coming to the WWF) was Rock (Blade Runner Rock, to be more exact.)
-Undertaker actually retired Shawn Michaels twice. The first time was unintentional and occurred as a result of back dropping him at the '98 Royal Rumble and landing Michaels back first on the edge of the casket, which is what caused the back problems that sent Michaels into a four year retirement. The second time was intentional, and occurred at Wrestlemania 26.
-Not a WWF/E-exclusive fact but rather one that includes both WWF and WCW. The Kliq is, as everyone knows, is the infamous backstage group that was comprised of Shawn Michaels, HHH, X-Pac, Kevin Nash and Scott Hall. The group played a huge role off-screen in the WWF during the New Generation Era when it came to backstage politics, and they also ended up playing a huge role on-screen in both companies during the Monday Night Wars. HHH and HBK formed D-Generation X in the WWF and Scott Hall and Kevin Nash ended up making up two-thirds of the original New World Order in WCW. And X-Pac ended up being apart of both groups - first the NWO (where he was known as Syxx), and then D-X when he jumped over to WWF in 1998.