[D17]

Sort of hinted at it at Wrestlemania 11. They said something along the lines of 'Undertaker's not lost at wrestlemania', something like that.

 

[Tombstoned]

It started being called a "streak" as such around Wrestlemania 17.

 

[#BadNewsSanta]

The first time I believe they played a storyline around it was Taker/Orton at WM21... but I can't recall the first time it was mentioned. I think WM17?

 

[DLane]

I wonder if at any time that there was a plan for him to never lose a Mania match? I guess with the exception of a few names he has been one of the very loyal workers in the WWE, maybe this is the reward?