The Kane you see today is a complete 180, from the man that first appeared back in 1997. Back then, the "long lost brother" of the Undertaker, who was brought in by father Paul Bearer, couldn't talk, had long hair, and wore a mask and body suit, which protected his apparently disfigured burnt face and body.
Oh yeah, I forget, Undertaker killed his parents, and burnt Kane, but they're good now.
Within a year of his debut, Kane was WWF Champion. He may have won it in a "First Blood" match wearing a mask, and it may have only lasted one day, but Kane was Champion, a fact the "E" never failed to let us forget for over a decade, before Kane finally won another.
Over the years, Kane's facade began to slip. First he could talk, then the body suit went away, finally the mask began to shrink, the mouth cover removed, no visible burns, shocker.
Finally Triple H decided it was his goal to completely destroy Kane. First the "Game" found out about "Katie Vick," apparently Kane lived a normal life and had a social life, let's just leave it at that. Then, HHH took Kane's I.C. Title, to unify it with the Heavyweight Title.
Lastly, if hadn't already done enough, he took Kane's mask, surprise he wasn't burnt, it was all in his head, more shockingly, Kane was bald, why he decided he needed a wig is a mystery that still remains.
It was strongly hinted in 2008 that Kane may return to his mask, but that never came to fruition, and instead he tried to take Rey Mysterio's mask.