Oscar Gutierrez (born December 11, 1974), better known by his ring name Rey Mysterio Jr. or simply Rey Mysterio (Spanish for "King Mystery"), is an American professional wrestler who is currently wrestling on the independent circuit. Mysterio is best known for his appearances with Extreme Championship Wrestling, World Championship Wrestling and WWE between 1995 and 2015, becoming a three-time world champion in the latter. Widely regarded as the greatest cruiserweight wrestler of all time,, Mysterio is known for his high-flying Lucha libre wrestling style, which is credited with having helped kick-start the emergence of cruiserweight wrestling in the United States in the mid-1990s. Championships held by Mysterio over the course of his career include WWE's World Heavyweight Championship, the WWE Championship, WCW/WWE Cruiserweight Championship, WCW World Tag Team Championship, WCW Cruiserweight Tag Team Championship, WWC World Junior Heavyweight Championship, WWE Tag Team Championship, and WWE Intercontinental Championship.

In 1999, after the two factions of nWo reformed, they demanded that the LWO disband. Mysterio refused to take off his LWO colors and was attacked by the nWo as a result. This led to a match at SuperBrawl IX where Mysterio and tag partner Konnan lost a "Hair vs. Mask match" against Kevin Nash and Scott Hall, forcing Mysterio to remove his mask. After the match, he phoned his uncle to tell him the news. Mysterio has publicly expressed his disappointment over being unmasked:  Mysterio later became a "giant killer" by defeating large opponents such as Kevin Nash, Bam Bam Bigelow, and Scott Norton. He faced Nash at Uncensored in a match where Lex Luger interfered and helped Nash in winning the match. Although he participated in several notable matches with some of the heavyweight top card wrestlers, it was made very clear to him that he would never receive a push to become a main eventer. This was due to Eric Bischoff utilizing cruiserweights as alternative, mid-card entertainment as opposed to the more conventional style that led WCW programming.  The next night on the March 15 Nitro, he defeated Billy Kidman to win his fifth Cruiserweight Championship. On the March 22 Spring Breakout episode of Nitro, Mysterio got his first shot at the WCW World Heavyweight Championship against champion Ric Flair when the names of (allegedly) nearly everyone in the company were put into a hat and a lottery was held. El Dandy was the lottery winner, but he was injured, and Mysterio took the shot instead. The match ended with a disqualification win for Flair, even though Arn Anderson's interference on Flair's behalf should have theoretically disqualified Flair. The following week, Mysterio and Kidman teamed with each other and defeated Flair's Four Horsemen stablemates Chris Benoit and Dean Malenko to win the WCW World Tag Team Championship, making Mysterio a double champion. Mysterio successfully defended his Cruiserweight Championship against his tag team partner Kidman at Spring Stampede before losing the title on the April 19 episode of Nitro to Psicosis in a Fatal Four-Way match that also involved Juventud Guerrera and Blitzkrieg. On the following episode of Nitro, he defeated Psicosis to win his fifth Cruiserweight Championship. At Slamboree, Mysterio and Kidman lost the World Tag Team titles to Raven and Perry Saturn in a Triangle match, also involving former champions Benoit and Malenko.

did he set any records?
Mysterio and Kidman lost the World Tag Team titles to Raven and Perry Saturn in a Triangle match,