Because the two actresses tended to play the same type of overwrought roles in the mid-1950s, juvenile stars Patty McCormick and Patty Duke were sometimes mistaken for one another during this period. But once seen in her starmaking role as the homicidal preteen Rhoda Penmark in The Bad Seed (in which she starred on Broadway in 1954 and in the film version in 1956), Patty McCormick can never be confused with anyone else. A pro from the age of four, McCormick was in films from 1951 and TV from 1953. After Bad Seed, she was second-billed as a bratty child star in the theatrical-film Kathy O' (1957) and was headlined in her own 1958 sitcom, Peck's Bad Girl. The uniqueness that characterized McCormick's appearances as a child evaporated when she reached maturity; though she was more than competent playing disturbed teenagers in films like The Miniskirt Mob (1967) and The Young Runaways (1968), these were parts that could have been played equally well by a dozen other young actresses. She acted sporadically into the 1970s and 1980s, her longest assignment being the role of Jeffrey Tambor's upwardly mobile wife on the TV sitcom The Ropers. In 1995, Patty McCormick starred in the direct-to-video Mommy, playing a grown-up edition of the murderous Rhoda from The Bad Seed.