One might argue that the very first time that the Undertaker's Wrestlemania Streak was a huge selling point was Wrestlemania 21, when Randy Orton took to the ring with the Undertaker, on April 3rd 2005 at Wrestlemania 21.
7 Days Until Wrestlemania 28A fun trivia fact for this match is that at one time, Randy Orton was intended to defeat the Undertaker at Wrestlemania 21, but Randy Orton respectively turned it down. Adding to the fact that he was injured shortly after Wrestlemania 21, it might not have been the best thing. Still there is an alternate universe out there with the Undertaker having lost against Randy Orton at Wrestlemania 21.
Randy Orton's babyface run from 2004-2005 was not the stirring success. After a brief run of World Heavyweight Championship and a failed feud with Triple H, it appeared that Batista's babyface turn was going to be held in a much higher regard. Therefore Randy Orton settled for a delightful consolation prize, that being the Undertaker's Wrestlemania undefeated streak. Randy Orton tapped into a brand new evil, the Legend Killer having returned. He took out his girlfriend Stacy Keibler with the RKO and then also WWE Legend Jake "The Snake" Roberts.
Randy Orton gave the Undertaker the fight on Wrestlemania night. Including with Orton's father, "Cowboy" Bob Orton coming out and nailing the Undertaker with a cast. After all of those years, the Cowboy's arm injury did not heal. The Undertaker survived the RKO and Orton tried to take down the Undertaker with his own Tombstone. This proved to be his downfall with the Undertaker reversing into the Tombstone Piledriver for the pin. 13-0 for the Undertaker.
Will the Undertaker reach 20-0 at Wrestlemania 28. Tune into Wrestlemania 28 to find out.