#1. He wrestled as Mark Callous in WCW before becoming The Undertaker in the WWE
Today it is hard to think of Mark Calaway as anything else other than The Undertaker, but he had actually gone through a number of gimmicks before stumbling upon the Deadman character on his arrival in the WWE.
The Commando, 'Mean' Mark Callous, Dice Morgan, The Master of Pain and Texas Red are just of the names he went by before striking gold as The Undertaker. He was actually on WCW before ever making it to the WWE. But his run as 'Mean' Mark Callous was so unmemorable that the company didn't have any problem letting him go to the WWE after just a year.
It is safe to say that 'Mean' Mark Callous would never go on to have a two-decade-long winning streak at Wrestlemania.