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William Michael "Billy" Zabka (born October 20, 1965) is an American actor, martial artist, screenwriter, and film producer. Zabka is best known for his role of Johnny Lawrence in The Karate Kid (1984), The Karate Kid Part II (1986), and decades later reprises the role of Johnny in the Netflix series Cobra Kai (2018-), along with Ralph Macchio as Daniel.

During the 1980s, Zabka appeared in the comedy movies Just One of the Guys (1985) and Back to School (1986). Zabka also co-starred on the CBS television series The Equalizer as the son of the title character (1986–89). He also played Jack, Audrey's jock boyfriend, in National Lampoon's European Vacation (1985).

During the 1990s and 2000s, he acted mostly in independent films while studying to be a filmmaker. In 2003, he wrote and produced the short film Most, shot on location in the Czech Republic and Poland. Most (aka The Bridge) had its world premiere at the Sundance Film Festival 2003 and won numerous awards at prestigious film festivals, including Best of Festival at the Palm Springs International Festival of Short Films in 2003. In 2004, he was nominated for an Academy Award for Most in the Live Action Short Film category.