Haas debuted on WWE's main roster on the December 26, 2002 episode of SmackDown! as a heel (villainous character) along with Shelton Benjamin as "Team Angle". The tag team was the "contingency plan" of Paul Heyman, and were intended to help WWE Champion Kurt Angle retain his title, attacking Chris Benoit and Brock Lesnar in an attempt to soften them up. They quickly won the WWE Tag Team Championship on February 6, 2003, by defeating Los Guerreros (Eddie and Chavo Guerrero). They held the championship for three months, including a successful title defense at WrestleMania XIX against Los Guerreros and the team of Chris Benoit and Rhyno, before losing the championship to Eddie Guerrero and his new partner Tajiri in a ladder match on May 18 at Judgment Day. On the June 12 episode of SmackDown, Angle fired Haas and Benjamin after they blamed him for losing the Tag Team Championship and began to question his leadership. The duo then dubbed themselves The World's Greatest Tag Team, although announcers made sure to add "Self Proclaimed" to the name. Haas and Benjamin regained the championship from Guerrero and Tajiri on the July 3 episode of SmackDown, but lost it to the reformed Los Guerreros on September 18. The team was separated when Benjamin was moved to the Raw brand as part of the 2004 Draft Lottery.
After Benjamin's draft, Haas turned into a fan favorite and gained Miss Jackie as a valet. He teamed with Rico to win the WWE Tag Team Championship on April 22, 2004. The pair lost the championship to the Dudley Boyz on June 17, and shortly afterwards, Haas became a singles wrestler, although he retained Miss Jackie as his valet. Haas lost a match to Luther Reigns at the Great American Bash.
Haas was later involved in an angle in which he was in a love triangle with Miss Jackie, who was acknowledged on-screen as his fiancée, and Dawn Marie. The storyline culminated when Haas served as the Referee in a match at Armageddon 2004 between the two women. After the match, Haas left both women in storyline, although he continued his relationship with Miss Jackie off-screen. In early-2005, he formed a tag team with Hardcore Holly. They were involved in a feud (scripted rivalry) with MNM for the WWE Tag Team Championship, but never won the championship.
On July 8, 2005, Haas was released by World Wrestling Entertainment along with his real-life wife Jackie Gayda.
Haas returned to WWE in 2006, appearing on the April 17, 2006, episode of Raw as Rob Van Dam's handpicked opponent for his former partner, Shelton Benjamin. Haas defeated Benjamin in the ensuing match. Haas continued to wrestle on the lower midcard spot, becoming a regular fixture on Heat.
On the June 5, 2006 episode of Raw, Haas inadvertently knocked Lilian Garcia off the ring apron as he was entering the ring. It was announced on WWE's official website that as a result, Garcia suffered a sprained wrist. As a result of the legitimate accident, Haas began a feud with Garcia's onetime storyline love interest Viscera. Haas made advances towards Garcia, at one point forcefully kissing her and then dropping her to the ground. Haas and Viscera continued to fight for Garcia's affection in the ring, until she told them both that she wanted to be "just friends". Haas gave Viscera an eye rake in anger, and a blinded Viscera accidentally gave Garcia a Samoan drop. Though it was unintentional, when both Haas and Viscera had seen what had happened to their now former love interest, they simply had a laugh about it, thus making Haas a villain. After that, Viscera and Haas became a tag team, competing on both Raw and Heat until splitting in December 2006.
After Shelton Benjamin won a match against Super Crazy on the December 4, 2006, edition of Raw, Haas came out to celebrate his win with a bewildered Benjamin. Haas and Benjamin announced the return of The World's Greatest Tag Team on the December 11, 2006 edition of Raw, and they defeated The Highlanders in their return match. They then started a feud with Cryme Tyme. They continued to compete on Raw through the start of 2007, facing teams including John Cena and Shawn Michaels and Ric Flair and Carlito. In mid-2007, The World's Greatest Tag Team feuded briefly with The Hardys in storyline; at the One Night Stand pay-per-view on June 3, 2007, they challenged The Hardys for the WWE World Tag Team Championship in a ladder match but were unsuccessful. The team broke up once again when Benjamin moved to the ECW brand on November 20, 2007.
Early in 2008, Haas developed a gimmick in which he would go under the ring in the middle of his matches and re-emerge wearing a mask. In this "alter-ego", Haas would sometimes perform luchador-esque maneuvers in a comical fashion (such as attempting a diving splash, but instead landing on his feet and hitting a standing splash). The opponent would often unmask Haas mid-match, returning him to his normal demeanor. During this persona, Haas usually competed in dark matches before the live broadcast of Raw or on Heat.
Beginning in late August, Haas turned into a face (heroic character) and began a storyline in which he began to impersonate other wrestlers. His first match under this gimmick was a loss to Carlito's real-life brother Primo Colón, while Haas was parodying Carlito with the name "Charlito". He has portrayed such superstars as John Cena, John "Bradshaw" Layfield, Jim Ross, The Great Khali, Montel Vontavious Porter, legends such as Stone Cold Steve Austin, Bret Hart, "Mr. Perfect" Curt Hennig, Jimmy "Superfly" Snuka, Rowdy Roddy Piper, Hulk Hogan and even WWE Diva Beth Phoenix for which he won a Slammy Award.
On April 15, 2009, Haas was drafted to the SmackDown brand as part of the 2009 Supplemental Draft. On the May 8, 2009 episode of SmackDown, Haas made his in-ring return to the brand as a heel, abandoning his persona of imitating other wrestlers, and losing to John Morrison in a match where he was accompanied by his former World's Greatest Tag Team partner, Shelton Benjamin. The following week on the May 15, 2009 episode of SmackDown, Benjamin and Haas unofficially reunited and competed against John Morrison and CM Punk in a losing effort, but Benjamin was traded to the ECW brand in June.
After an absence of several months, Haas made his return to television by teaming with Mike Knox in a losing effort against Cryme Tyme on the December 31, 2009 episode of Superstars. On February 28, 2010, WWE announced that Haas had been released from his contract.