Rey Mysterio lost his mask at WCW SuperBrawl IX in 1999 when he and Konnan were defeated by The Outsiders (Kevin Nash & Scott Hall).
Mysterio was without his mask for the rest of his WCW tenure, which ended on the final Nitro with Mysterio teaming with Billy Kidman to win the Cruiserweight Tag Team Titles from Elix Skipper and Kid Romeo.
When Mysterio made his WWE debut in 2002, the mask returned.
"Prior to coming to WWE, I was in OVW training, which was a week prior to my debut and the office wanted to see the gear I wanted to use. When I showed it to them, I had no mask. They were like, 'Where is the mask?' 'Well, I lost the mask.' In Lucha Libre, if you lose the mask, you never put it back on. They were like, 'No, Vince wants you to come back with the mask.' 'I'm glad you told me now because it would have sucked if you told me the day of.' I had an outfit made with the mask and that was history. The mask was a very important piece of my career in WWE. If WCW didn't market the mask the correct way, I knew Vince would," Mysterio told Ryan Satin on Out of Character. "In Mexico, when I went for the first time with WWE, they didn't want me to wrestle with the mask on because I had lost it. I had been wrestling with it since I signed with WWE, but they didn't care. At the end of the night, they were like, 'it's cool.'"
WWE has marketed Mysterio as the Greatest Mask Of All-Time. Mysterio is one-half of the SmackDown Tag Team Champions alongside his son Dominik.
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