Undertaker

In 1989, Calaway joined World Championship Wrestling as a villain and adopted the ring name Mean Mark Callous, a name devised for him by Terry Funk.[15] He was portrayed as a morbid character; he wore predominantly black ring attire, and was described by announcer Jim Ross as having a fondness for pet snakes, and the music of Ozzy Osbourne. Callous was promptly drafted into the Skyscrapers tag team to replace an injured Sid Vicious. The new team gained some notoriety at Clash Of The Champions X when they beat down The Road Warriors after their match. However Callous' partner Dan Spivey left WCW days before their Chicago Street Fight against the Warriors at WrestleWar 1990. Callous and a replacement masked Skyscraper went down to defeat in the Street Fight and the team broke up soon afterwards. As he went into singles competition, Callous took on the guidance of Paul E. Dangerously and defeated Johnny Ace at Capital Combat and defeated Brian Pillman at the Clash of the Champions. In July 1990, he wrestled against Lex Luger for the NWA United States Heavyweight Championship at The Great American Bash, but was pinned by Luger. WCW declined to renew Calaway's contract.

Calaway then briefly wrestled in New Japan Pro Wrestling as Punisher Dice Morgan. After leaving, he briefly returned to the USWA to participate in a tournament to determine the new USWA Unified World Heavyweight Champion; he defeated Bill Dundee in the first round, but lost to Jerry Lawler in the quarterfinals. In October 1990, he signed with the World Wrestling Federation (WWF).