In 2005, Crazy signed a contract with World Wrestling Entertainment (WWE). He initially appeared at the WWE-promoted ECW One Night Stand on June 12, 2005 winning an international three-way dance by pinning Yoshihiro Tajiri in the final pinfall of the match. During the match, he performed a moonsault from a second story balcony.
Crazy's first appearance on WWE television came during the June 18, 2005 airing of SmackDown!'s sister show WWE Velocity, teaming with Psicosis to defeat Akio and Billy Kidman. Psicosis, Super Crazy, and Juventud grouped together to form a stable known as The Mexicools. The group made their debut as heels on the June 23, edition of SmackDown! when all three members rode to the ring on John Deere lawn mowers with the decals altered to say Juan Deere (John in Spanish) and wearing matching coveralls. They then attacked Chavo Guerrero and Paul London during their WWE Cruiserweight Championship match. Juventud cut a promo questioning the lack of "true Mexican luchadores" in the Cruiserweight Division, before going on to deride the current state of Mexican Americans in general. Psicosis dubbed the lawnmower they arrived on a "Mexican Limo 2005" and the group claimed that even Mexico's President mocks Mexicans in the United States (in reference to Vicente Fox's controversial remark that Mexican immigrants do the jobs "not even the blacks want to do"). Juventud then stated that they were "no longer there to clean toilets and work for "them" (the "gringos") but "they" were going to be working for "us" (The Mexicools)", before dubbing the team "not Mexicans but Mexicools!" In the following weeks, they continued to interfere in matches and mock the stereotypical image of Mexicans in the United States.Despite being introduced as heels, the group quickly became favorites of the audience and eventually began acting as faces. They received strong approval from the audience even during their debut, which occurred in Tucson, Arizona. On July 24 at The Great American Bash, Psicosis pinned Stevie Richards to secure the Mexicools' first PPV win in a six-man tag match with the bWo. During December 2 edition of SmackDown!, Super Crazy and Psicosis competed in an over the top rope battle royal against 5 other tag teams. The pair managed to win and earned themselves a match against MNM at Armageddon for the WWE Tag Team Championship. Unfortunately for the Mexicools, MNM lost the tag team titles before their match. Not long after, Super Crazy and Psicosis became the only Mexicools left in WWE, as Juventud was released from WWE on January 6, 2006. Super Crazy and Psicosis continued to wrestle as a tag team, but Crazy got his own push as a singles competitor, eventually earning himself #1 contendership for the WWE Cruiserweight Championship. By June, 2006 Super Crazy's partnership with Psicosis on SmackDown! began to crumble when Psicosis repeatedly abandoned Crazy during incidents with a monster heel known as The Great Khali. This resulted in the pairing splitting up and then engaging in a short-lived feud after Psicosis turned heel. After the breakup, both Psicosis and Super Crazy disappeared off WWE programming.
On September 4, Super Crazy made his Raw debut with a victory over Chris Masters using his trademark moonsault. Crazy continued his feud with Masters throughout September, defeated him once more and competing with Masters, along with four other wrestlers (Johnny Nitro, Carlito, Jeff Hardy and Charlie Haas) in a Six-Pack Challenge Match for the WWE Intercontinental Championship on the September 18 edition of Raw, which neither Masters or Crazy were able to win. Crazy was then involved in angles with Nitro and Melina, during which he was aligned with Mickie James, who was feuding with Melina at the time.
Super Crazy suffered an injury to his left knee at a house show which occurred on April 21, 2007 in Oberhausen, Germany. The injury was believed to be a MCL tear. Super Crazy returned to action on June 1 in a match taped for Heat, losing to the returning William Regal. On the July 2 edition of Raw, Super Crazy was Mr. Kennedy's opponent in a Beat the Clock match. Before the match began, Super Crazy appeared to have agreed to let Kennedy win, however he defeated Kennedy with a roll-up shortly after the match began, while Kennedy was performing his introduction. Kennedy assaulted Super Crazy later that night. Kennedy then defeated Super Crazy in a grudge match two weeks later. In October 2007, Super Crazy formed a tag team with Jim Duggan. The team primarily competed on Heat to moderate success until Supre Crazy was drafted to the ECW brand.
As part of the 2008 WWE Supplemental Draft, Super Crazy was drafted to the ECW brand. Super Crazy returned to SmackDown (although wearing an ECW shirt), losing to The Brian Kendrick. On the August 19 edition of ECW on Sci-Fi, Super Crazy debuted on the ECW brand, teaming with Evan Bourne and Tommy Dreamer in a losing effort to John Morrison, Chavo Guerrero and The Miz. On October 17 edition of SmackDown!, he was defeated by The Brian Kendrick's bodyguard, Ezekiel Jackson. The following week he was defeated by The Brian Kendrick as well, in what turned out to be his last televised match with WWE. On November 5, 2008 World Wrestling Entertainment announced on their website that Pantoja had been released from his WWE contract. According to the latest edition of the Wrestling Observer Newsletter, Pantoja asked for his release on November 1 as he was unhappy with his place in the company.