When the Undertaker was doing the American Badass gimmick, he spoke a lot more and made the gimmick a reflection of his real-life personality. In 2002, he was a full-fledged heel, who destroyed whomever he wanted, which included Ric Flair at WrestleMania X-8. Another thing that was going on at that time, and also continues to this day, is the WHAT chants, aimed at anyone in the ring who bores the fans with their promos. What was supposed to be a catchy Steve Austin expression morphed into an insult at wrestlers, as fans would often chant this when a promo had easy pauses, or when fans wanted to mess with whoever was speaking in the ring. Undertaker, getting irritated at the fans chanting this during his promo, found a perfect way to get the fans to shut up: https://www.youtube.com/watch?v=G6J4hpy_8h8&feature=youtu.be Say WHAT if you like to sleep with your own sister Taker ad-libs that line so well that most of the fans dont have enough time to react, so a large number of them end up falling into his trap, and said WHAT as he shook his head in disappointment. It was one of the funniest moments by a wrestler whos known for being stoic and otherwise very serious. Undertaker doesnt do comedy very often, if ever, so seeing him say something funny at random makes this one of the best ad-libs in recent memory. It goes to show that if theres anyone who can stop the annoying WHAT chants, its the Undertaker.