In 2005, Castellanos signed a contract with World Wrestling Entertainment (WWE).
He appeared at the WWE promoted ECW One Night Stand pay-per-view on June 12, losing to Rey Mysterio.
His first WWE television appearance was on the June 18 airing of WWE Velocity, teaming with Super Crazy to defeat Akio and Billy Kidman.
Psicosis, Super Crazy, and Juventud grouped together to form a faction known as The Mexicools.
The group made their debut as heels on June 23 when all three members rode to the ring on a John Deere lawn mower, with the sticker saying Juan Deere to be more Mexican, wearing matching coveralls and attacked both 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 state of Mexican Americans in general.
Psicosis dubbed the lawn mower they arrived on a "Mexican Limo 2005" and the group claimed that even Mexico's President mocks Mexicans in the United States; this referenced Vicente Fox's controversial remark that Mexican immigrants do the jobs "not even the blacks want to do."
Guerrera 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 would continue to make run-ins in matches and mock the stereotypical image of Mexicans in the United States, even coming to the ring each with their own riding lawn mower.

On July 24 at The Great American Bash in Buffalo, New York, they defeated The Blue World Order in a six-man tag match when Psicosis pinned Steven Richards to secure the Mexicools' first pay-per-view win.
The trio then turned face by feuding with Nunzio and Vito.
During the December 2 episode of SmackDown!
Super Crazy and Psicosis won a battle royal with 5 other tag teams, earning a match against MNM at Armageddon 2005 for the WWE Tag Team Championship.
MNM lost the titles before their match, however, which meant that the Armageddon match was just a standard tag team match.
During the January 27, 2006 episode of SmackDown!
Super Crazy and Psicosis defeated The Dicks (Chad Wicks and John Toland) and the F.B.I. in a three-way tag team match to win spots in the 2006 Royal Rumble match on January 29.
Psicosis entered at #4 in the Royal Rumble match but was quickly eliminated by his former WCW rival Rey Mysterio.
During June 2006 the ECW brand was revived and with this came the expectations that Super Crazy would leave Psicosis and SmackDown!
for the new ECW brand.
This was later fueled with a match that would see Yoshihiro Tajiri and Super Crazy team up and face the F.B.I. at One Night Stand.
At this time, Psicosis' partnership with Crazy began to crumble when Psicosis abandoned Crazy during incidents with The Great Khali.
The team split up, with Psicosis turning heel.
On the July 21 episode of SmackDown, Psicosis lost to Super Crazy.
This was Psicosis' last WWE appearance.
After a four-month inactivity, WWE announced that Castellanos was released from WWE in the fall of that year because of his arrest in Mexico on November 1, 2006.
In 2005, Castellanos signed a contract with World Wrestling Entertainment (WWE). He appeared at the WWE promoted ECW One Night Stand pay-per-view on June 12, losing to Rey Mysterio. His first WWE television appearance was on the June 18 airing of WWE Velocity, teaming with Super Crazy to defeat Akio and Billy Kidman. Psicosis, Super Crazy, and Juventud grouped together to form a faction known as The Mexicools. The group made their debut as heels on June 23 when all three members rode to the ring on a John Deere lawn mower, with the sticker saying Juan Deere to be more Mexican, wearing matching coveralls and attacked both 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 state of Mexican Americans in general. Psicosis dubbed the lawn mower they arrived on a "Mexican Limo 2005" and the group claimed that even Mexico's President mocks Mexicans in the United States; this referenced Vicente Fox's controversial remark that Mexican immigrants do the jobs "not even the blacks want to do." Guerrera 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 would continue to make run-ins in matches and mock the stereotypical image of Mexicans in the United States, even coming to the ring each with their own riding lawn mower.
On July 24 at The Great American Bash in Buffalo, New York, they defeated The Blue World Order in a six-man tag match when Psicosis pinned Steven Richards to secure the Mexicools' first pay-per-view win. The trio then turned face by feuding with Nunzio and Vito. During the December 2 episode of SmackDown! Super Crazy and Psicosis won a battle royal with 5 other tag teams, earning a match against MNM at Armageddon 2005 for the WWE Tag Team Championship. MNM lost the titles before their match, however, which meant that the Armageddon match was just a standard tag team match. During the January 27, 2006 episode of SmackDown! Super Crazy and Psicosis defeated The Dicks (Chad Wicks and John Toland) and the F.B.I. in a three-way tag team match to win spots in the 2006 Royal Rumble match on January 29. Psicosis entered at #4 in the Royal Rumble match but was quickly eliminated by his former WCW rival Rey Mysterio. During June 2006 the ECW brand was revived and with this came the expectations that Super Crazy would leave Psicosis and SmackDown! for the new ECW brand. This was later fueled with a match that would see Yoshihiro Tajiri and Super Crazy team up and face the F.B.I. at One Night Stand. At this time, Psicosis' partnership with Crazy began to crumble when Psicosis abandoned Crazy during incidents with The Great Khali. The team split up, with Psicosis turning heel. On the July 21 episode of SmackDown, Psicosis lost to Super Crazy. This was Psicosis' last WWE appearance. After a four-month inactivity, WWE announced that Castellanos was released from WWE in the fall of that year because of his arrest in Mexico on November 1, 2006.
Psicosis