Beginning in 1998, Guerrera pinned Último Dragón to win the Cruiserweight Championship on the inaugural edition of "Thunder" on January 8, 1998. However, he would then lose the title to Rey Misterio Jr. one week later on the following edition of "Thunder". At SuperBrawl VIII, Guerrera challenged Chris Jericho for the title in a mask vs. title match, in which Guerrera lost forcing him to unmask. After unmasking Guerrera, Jericho would often berate Guerrera for his looks by referring to him as "Quasi-juice" which was in reference to "Quasimodo", the disfigured lead character in "The Hunchback of Notre Dame". Later in the year, Guerrera defeated Jericho at Road Wild to capture his second Cruiserweight Championship. He retained the belt at Fall Brawl against Silver King, before losing to Billy Kidman the following night on "Nitro".