After WCW was purchased by the WWF in March 2001, Moore signed a contract with the WWF and was assigned to the Heartland Wrestling Association, an Ohio-based WWF developmental territory. He teamed with Karagias in HWA until Karagias was released by the WWF. In July 2002, Moore was promoted to the primary WWE roster and assigned to the SmackDown! brand.
Moore competed in the cruiserweight division for several months before becoming an acolyte of Matt Hardy Version 1.0, then proselytizing a philosophy known as "Mattitude". Moore became a "Mattitude Follower" (abbreviated to "MF'er"), and began dressing like Hardy and accompanying him to ringside. Moore would often unsuccessfully attempt to help Hardy win matches, resulting in Hardy attacking Moore in order to vent his frustrations, or would lose to a more physically dominant opponent, with Hardy again assaulting Moore as a result, claiming that he had failed to comprehend Hardy's coaching. Moore also assisted Hardy in his bid to win the 2003 Royal Rumble, again unsuccessfully, and helped Hardy lose several pounds in order to qualify for a WWE Cruiserweight Championship title shot. On February 23, 2003 at No Way Out, Moore distracted Crusierweight Champion Billy Kidman, enabling Hardy to pin him and win the title.
On April 24, 2003, Crash also became an MF'er, and was also referred to as being a "Moore-on". The stable was short-lived, as Crash was released from WWE on June 30.
Moore and Hardy continued to work together until November 17, when Hardy left SmackDown! and joined the RAW brand. As a result, Paul Heyman (the SmackDown! general manager) decided to punish Hardy for leaving his show vicariously by forcing Moore to face a series of much larger opponents. In successsive weeks, Moore was squashed by Matt Morgan, Nathan Jones and The Big Show before unexpectedly defeating A-Train in an upset victory on the December 11, 2003, episode of SmackDown!. The following week, WWE Champion Brock Lesnar was scheduled to defend his title against a random wrestler, with the name of his opponent selected arbitrarily by a lottery machine. Moore was selected as Lesnar's opponent, and Lesnar defeated him with ease, then revealed that all the balls had borne Moore's named, with Lesnar having rigged the process in order to ensure that he would have a much smaller opponent. Immediately after the match, Moore and Hardcore Holly were scheduled to face A-Train and Matt Morgan in a tag team match, with Holly gaining a title shot if he won and being fired if he lost. Despite Moore being incapacitated, he and Holly were able to win the match.
At WrestleMania XX on March 14, 2004, Moore took part in a battle royal for the Cruiserweight Championship, but was eliminated by Jamie Noble. His next high profile appearance was on the July 8, 2004, episode of SmackDown!, which saw Moore wrestle under a mask as El Gran Luchadore. Moore faced John "Bradshaw" Layfield in the match for the WWE Championship, and was initially dominated by his much larger opponent. However, a second Luchadore (the disguised Eddie Guerrero) took Moore's place, prompting Layfield to run away, thus giving Moore the victory by count-out.
Moore competed in the cruiserweight division and as a jobber for the remainder of 2004 and the first half of 2005. In early 2005 he adopted the gimmick of "The Prince of Punk", and began wearing punk clothing to the ring. On March 21, 2005, he was concussed and suffered Whiplash after his hummer was involved in a head-on collision with a vehicle driven by an inebriated United States Army Sergeant in Fort Bragg, North Carolina. He quickly recovered from his injuries, but was fired by WWE on July 5, 2005.
Moore returned to the independent circuit soon thereafter, although the no-compete clause in his contract (which prohibits WWE employees who are fired or who negotiate a contract release from appearing on television within a given time period) did not expire until November 1 of that year. He also opened a professional wrestling school known as the "School of Punk".
