It's been said that had anyone else been chosen to play the gimmick of The Undertaker, the character may not still be around today. Mark Calaway has constantly tweaked the famous persona, keeping it relevant even as he nears the end of his active in-ring career. Even at 50 years of age, Calaway is still a vital part of the WWE product, and it's unimaginable to picture the company without him. Absolutely nobody could have predicted the success the gimmick would have when it first appeared way back in 1990. Moving slowly, like he was walking through treacle, The Undertaker's matches were far from exciting. Instead, it was the visual horror that 'Taker carried with him, and the sheer mystical force of the gimmick itself. Actual wrestling wasn't what Undertaker was all about in the early years. In the mid-90's, Calaway made the decision to quicken the pace, and it proved to be a shrewd move. The zombie-like movements had grown tiresome, and things needed to go in a different direction if The Undertaker was going to survive. More so than in-ring performances, Calaway's biggest achievement has been ensuring Undertaker appeals to each passing generation of wrestling fan.