He debuted at Survivor Series 1990, but he use to be in wcw before joing wwf
here some info on the deadman
What was the story behind the Undertaker "dying" in 1994?
At the end of 1993 The Undertaker began to feud with Yokozuna. At Royal Rumble 1994 they fought in a casket match for the world title. The Undertaker was about to win the match when 10 heel wrestlers interfered and helped Yokozuna put Undertaker in the casket to win.
After the match Undertaker appeared on the big video screen and gave a short speech on how he would not rest in peace and would return for revenge. After the speech the lights went out and Marty Jannetty dressed as The Undertaker was raised up to the roof of the arena in the crucifix position giving the angle that Undertaker ascended to heaven.
In real life Mark Calloway just needed time off to handle some family matters. He didn't actually die!
Who was the Fake Undertaker?
About 5 months after the Undertaker "died" at Royal Rumble Ted Dibiase began claiming on WWF television that he had the Undertaker. Paul Bearer came out weeks later and said he had the Undertaker and that Dibiase that lying. A match was signed for Summerslam 1994 for the two Undertakers to fight each other to see how actually had the real one.
Paul Bearer had the real Undertaker of course and Ted Dibiase just had Brian Lee dressed as the Undertaker. Undertaker beat Brian Lee at Summerslam with three tombstones and the Fake Undertaker was never seen and barely talked about on WWF television again.