When he first signed with World Wrestling Entertainment (WWE), Bob Holly was given the gimmick of a NASCAR racer turned wrestler named Thurman "Sparky" Plugg. This gimmick was partly based on Holly's real-life interest in NASCAR racing. The name of the gimmick was later changed to Bob "Spark Plug" Holly. Holly competed with this gimmick without any further success except an unrecognized WWE Intercontinental Championship reign and a one-day WWF Tag Team Championship reign until 1998, when he joined the J.O.B. Squad, a stable with "subtle" references to jobbing led by Al Snow. To accommodate this new gimmick, Holly dyed his naturally dark hair blonde and wore the trademark "Pin me, pay me" shirt worn by other members of the stable.
In 1999, Bob Holly, with shaved hair and new attire joined the hardcore division of WWF, feuding with Al Snow, his former leader and successfully winning the WWF Hardcore Championship from him at St. Valentine's Day Massacre. Shortly thereafter, Holly's ringname was changed to Hardcore Holly, reflecting his prowess with weapons in matches and his ability to take pain. This gimmick would usually be portrayed as a tweener. Holly achieved his greatest success with this gimmick, amassing a total of six Hardcore Championship reigns and competing in countless hardcore matches, including two championship wins at WrestleMania events.
After the disbandment of the hardcore division and the retirement of the Hardcore Championship, certain facets of the Hardcore Holly character were tweaked. His character was pushed as that of a tenured veteran of the company, often playing the bully for Vince McMahon and giving rookies a hard time, like in his feuds with Maven and Randy Orton. Even after the disbandment of the hardcore division and the receding frequency of hardcore matches in WWE, Hardcore Holly occasionally wrestles in weapon stipulation matches, his last singles match under hardcore rules being an Extreme Rules match against Rob Van Dam in 2006, where he infamously sliced open his back and continued to wrestle the match, one of Holly's most memorable moments in the opinion of many fans.