The duo was formed in 1993 as heels when Shawn Michaels lost the WWF Intercontinental Championship to his former tag team partner, Marty Jannetty on May 17, 1993 edition of RAW (thanks to Mr. Perfect who interfered when he threw a towel into Shawn's face which helped Marty roll up Shawn in the small package and the win).
Michaels brought Nash to the WWF as his heel bodyguard Diesel during early 1993. He helped Michaels win the Intercontinental Championship from Jannetty on June 6, 1993 at a House show. He helped Michaels defend it for 4 months until WWF President Jack Tunney suspended and stripped him of the title. In reality, Michaels tested positive for steroids and was suspended by Vince McMahon for six weeks.
Razor Ramon won the title after being one of the two survivors of the RAW Battle Royal and defeating the other survivor of the Battle Royal, Rick Martel, the following week. When Shawn returned, he went after Razor Ramon and tried to steal it, and they created his own Intercontinental Title since Shawn felt that he was still champion because he never lost the title. This led the two to facing each other in a Ladder match at WrestleMania X to determine who was the undisputed Intercontinental champion. Despite help from Diesel, Razor Ramon beat Shawn and retained his Intercontinental Belt. Soon after Shawn's failure to recapture the IC belt, Diesel went after Ramon's title. On April 13, 1994 edition of Superstars, Diesel captured the WWF Intercontinental Championship from Ramon when Michaels interfered.
A day before Diesel's match with Razor Ramon at SummerSlam 1994, Michaels and Diesel teamed up to take on The Headshrinkers (Samu and Fatu) for the WWF Tag Team Championship, which they won, making Diesel a double champion. At SummerSlam, Diesel lost the Intercontinental Title to Razor Ramon when Shawn accidentally hit him with Sweet Chin Music. However this turned out to be a betrayal when Michaels said in a storyline interview that Diesel was nothing without him. Michaels and Diesel would vacate the WWF Tag Team Championship in November 1994 due to dissention between them.
After Shawn won the 1995 Royal Rumble, he faced Diesel at WrestleMania XI. Michaels brought in Sycho Sid as his new bodyguard but lost the match despite Sid's interference. The next night on RAW, when Shawn announced that he would give his bodyguard the night off during a rematch, Sid attacked Michaels until Diesel came to the rescue.
A couple of months later, Shawn went on to recapture the WWF Intercontinental Championship this time from Jeff Jarrett. A month or two later, the two reteamed and called themselves, Two Dudes with Attitude. At In Your House 3, Michaels and Nash faced the tag team champions, Owen Hart and Yokozuna in a Triple Crown Match. The rules were that if Michaels or Diesel beat Yokozuna or Owen, they would win the tag titles, but if Yokozuna or Owen beat either Michaels or Diesel, then that person who pinned or submitted that champion would gain their title (either Michaels' Intercontinental Belt or Diesel's World Title). However, The British Bulldog substituted for Owen Hart, who hadn't arrived at the building. During the match, Owen Hart appeared out of nowhere during the match and was pinned. Michaels and Diesel were awarded the championship, but since Owen was not officially part of the match, the titles were returned to Owen and Yokozuna the following night.
The team broke up again after Diesel lost his title to Bret Hart at Survivor Series 1995 and Shawn eliminated Diesel to win the 1996 Royal Rumble. After Shawn won the belt from Bret at WrestleMania XII, the two faced off a month later at In Your House 7: Good Friends, Better Enemies in a No Disqualification match for the WWF Title. Shawn retained the title after he hit Diesel with Sweet Chin Music.
The two faced each other one more, this time in a Steel Cage match. Michaels won because this was Kevin Nash/Diesel's last night with the WWF. After the match Shawn Michaels, Diesel (Kevin Nash), Razor Ramon (Scott Hall) and Hunter Hearst Helmsley hugged and said their farewells to each other.
Michaels and Nash did not reunite until June 3, 2002 when Kevin Nash named Shawn Michaels as the newest member of the nWo. On the June 10 edition of Raw, Michaels explained his best friend, Kevin Nash was always there for him, which was why he returned to WWE to become a member of the nWo. He then shocked the audience by Superkicking Booker T out of the nWo.
A month later, Nash tore his quadriceps, which broke up the nWo. When Nash returned from his injury, the duo faced Evolution (Triple H, Ric Flair and Randy Orton) in an effort to have Nash win the World Heavyweight Championship from Triple H. At Judgment Day 2003, Nash came close to winning the title until Triple H got himself disqualified when he hit referee Earl Hebner with the sledgehammer in the chest. This did not stop Nash, as he eventually Jacknife Powerbombed Triple H through the announcers' table. Nash later left the WWE soon after SummerSlam 2003 when he was the first to be eliminated in the Elimination Chamber match after Shawn hit him with Sweet Chin Music.
At the 2011 WWE Hall of Fame ceremony, Nash appeared on stage after Michaels had been inducted, alongside fellow Kliq members Triple H and Sean Waltman (X-Pac).