For those that don't remember HBK and The Undertaker in the past, their first feud dated back in the fall of 1997.  Where they got to be involved in the first ever Hell In A Cell match which also involved the debut of the masked Kane and only one day after Brian Pillman passed away at the age of 35 from heart failure.  I was an In You House that fans back them will remember for a long time.

Shawn Michaels did win the match thanks to Kane's interference and back then he was also the holder of the now defunct European Champion.

Another notable one on one was the time when they were the last two remaining in the 2007 WWE Royal Rumble and The Undertaker tossed HBK over the top rope and made him an automatic #1 contender for WrestleMania.

Will the Undertaker go 17-0 on April 5?  He doesn't even want to think about his undefeated WrestleMania streak.  Perhaps HBK might repeat the feat which he did to end Ric Flair's career last year and may give the Undertaker his first ever WrestleMania loss?

I'm sure it will be a match to witness, and we have no idea how it will come about.  But that's how the storyline keeps fans making constant guesses.