This bright, wholesome young performer won the coveted role of Danny Madigan, the 11-year-old protagonist of the spectacular Arnold Schwarzenegger box-office flop, "The Last Action Hero" (1993). O'Brien entered show business as a model and actor, appearing in over 40 TV commercials and magazine ads. He made his feature debut in the Stephen King-inspired sci-fi thriller, "The Lawnmower Man" (1992) and reprised the role in the tepid sequel "Lawmower Man 2: Beyond Cyberspace" (1996). O'Brien also appeared in Charles Band's "Prehysteria!" (1993), a low-budget dinosaur epic partly inspired by "Jurassic Park", "My Girl 2" (1994) and "The Baby-sitter's Club" (1995). He made his TV series debut as Gerald McRaney's son in the CBS drama "Promised Land" (1996-99).