In 1984, Castillo was hired to play drums for Lita Ford and was featured on her "Dancin' on the Edge" album. Ford introduced Castillo to her boyfriend, Mötley Crüe bassist Nikki Sixx, and Nikki’s bandmate Tommy Lee. Shortly after the “Dancin’ on the Edge” tour, Lee called Castillo from a party he was at with Ozzy Osbourne and told him Ozzy was looking for a new drummer. Despite being unable to audition right away due to a broken leg he suffered while skiing, Castillo was hired by Osbourne a couple months later and ended up staying with the Ozzy Osbourne band for ten years, recording five albums with Ozzy during that time: "The Ultimate Sin" (1986), "No Rest for the Wicked" (1988), "Just Say Ozzy" (1990), "No More Tears" (1991), and a double-disc live album, "Live & Loud" (1993).